remove signup page promotion checkbox; fix link (#304)

ui/src/pages/signup.tsx

@@ -1,6 +1,6 @@
 import { useEffect, useState } from "react";
 
-import { useNavigate } from "react-router-dom";
+import { Link as ReactLink, useNavigate } from "react-router-dom";
 
 import Avatar from "@mui/material/Avatar";
 import Button from "@mui/material/Button";
@@ -159,12 +159,6 @@ export default function SignUp() {
                 // helperText={formik.touched.password && formik.errors.password}
               />
             </Grid>
-            <Grid item xs={12}>
-              <FormControlLabel
-                control={<Checkbox value="allowExtraEmails" color="primary" />}
-                label="I want to receive inspiration, marketing promotions and updates via email."
-              />
-            </Grid>
           </Grid>
           <Button
             type="submit"
@@ -177,7 +171,7 @@ export default function SignUp() {
           {error && <Alert severity="error">{error}</Alert>}
           <Grid container justifyContent="flex-end">
             <Grid item>
-              <Link href="#" variant="body2">
+              <Link component={ReactLink} to="/login">
                 Already have an account? Sign in
               </Link>
             </Grid>