updating upgradability article and o1js audits list

docs/zkapps/o1js/index.mdx

@@ -60,7 +60,7 @@ Start your o1js journey by learning about [basic zk programming concepts](/zkapp
 
 ## Audits of o1js
 
-* **Third-party audit (Q1/Q2 2024)**. An audit by an external security firm is ongoing and on track to complete in Q2 2024. Results will be shared when available.
+* [**Veridise external audit (Q3 2024)**](https://github.com/o1-labs/o1js/blob/a09c5167c4df64f879684e5af14c59cf7a6fce11/audits/VAR_o1js_240318_o1js_V3.pdf).  We engaged Veridise, a security auditing company, to do a full audit of o1js version 1.  Veridise spent 39 person-weeks reviewing o1js in depth, and all issues of medium severity and higher were fixed.
 
 * [**Internal audit (Q1 2024)**](https://github.com/o1-labs/o1js/files/15192821/Internal.o1js.audit.Q1.2024.pdf). In March 2024, the o1js team spent roughly two person-weeks to conduct an internal audit of parts of the o1js code base. The audit focused on reviewing core provable code. A number of issues were found and fixed.
 

docs/zkapps/writing-a-zkapp/feature-overview/upgradability.mdx

@@ -89,14 +89,11 @@ const contractAddress = zkAppKey.toPublicKey();
 const upgradeTx = await Mina.transaction({ sender, fee },
   async () => {
     const update = AccountUpdate.createSigned(contractAddress);
-    update.update.verificationKey = {
-      isSome: Bool(true),
-      value: verificationKey,
-    };
+    update.account.verificationKey.set(verificationKey);
   }
 );
-await tx.sign([senderKey, zkAppKey]).prove();
-await tx.send();
+await upgradeTx.sign([senderKey, zkAppKey]).prove();
+await upgradeTx.send();
 ```
 
 And just like that, when the transaction is applied to the blockchain, the verification key at the ZkApp address will be updated from `"27729068461170601362912907281403262888852363473424470267835507636847418791713"` to `"18150279532259194644722165513074833862035641840431153413486908511595437348455"`!
@@ -149,14 +146,11 @@ const contractAddress = zkAppKey.toPublicKey();
 const upgradeTx = await Mina.transaction({ sender, fee },
   async () => {
     const update = AccountUpdate.createSigned(contractAddress);
-    update.update.verificationKey = {
-      isSome: Bool(true),
-      value: verificationKey,
-    };
+    update.account.verificationKey.set(verificationKey);
   }
 );
-await tx.sign([senderKey, zkAppKey]).prove();
-await tx.send();
+await upgradeTx.sign([senderKey, zkAppKey]).prove();
+await upgradeTx.send();
 ```
 
 ### State Variables

examples/zkapps/feature-overview/src/upgradability/upgrade.test.ts

@@ -71,10 +71,7 @@ test('Initial contract data has correct state', async () => {
 
 tx = await Mina.transaction({ sender: feepayerAddress, fee }, async () => {
   const update = AccountUpdate.createSigned(zkApp.address);
-  update.update.verificationKey = {
-    isSome: Bool(true),
-    value: v2Contract.verificationKey,
-  };
+  update.account.verificationKey.set(v2Contract.verificationKey);
 });
 await tx.sign([senderKey, addKey]).prove();
 await tx.send().wait();
@@ -100,10 +97,7 @@ test('Initial contract data has correct state', async () => {
 
 tx = await Mina.transaction({ sender: feepayerAddress, fee }, async () => {
   const update = AccountUpdate.createSigned(zkApp.address);
-  update.update.verificationKey = {
-    isSome: Bool(true),
-    value: v3Contract.verificationKey,
-  };
+  update.account.verificationKey.set(v3Contract.verificationKey);
 });
 await tx.sign([senderKey, addKey]).prove();
 await tx.send().wait();
@@ -158,10 +152,7 @@ test('Initial contract data has correct state', async () => {
 
 tx = await Mina.transaction({ sender: feepayerAddress, fee }, async () => {
   const update = AccountUpdate.createSigned(unsafeAddAddress);
-  update.update.verificationKey = {
-    isSome: Bool(true),
-    value: v3ContractUnsafe.verificationKey,
-  };
+  update.account.verificationKey.set(v3ContractUnsafe.verificationKey);
 });
 await tx.sign([senderKey, unsafeZkAppAccount.key]).prove();
 await tx.send().wait();