Update link in c#.md #15782

Job	Run time
Sqlc check	5m 15s
RPC and mobile compilation check	5m 33s
cross compilation	34m 13s
check commits	5m 26s
lint code	7m 32s
sample configuration check	4m 7s
check pinned dependencies (google.golang.org/grpc v1.59.0)	5s
run macOS itest	50m 41s
check pinned dependencies (github.com/golang/protobuf v1.5.3)	4s
check release notes updated	5s
run ubuntu itests (btcd, backend=btcd cover=1)	34m 30s
run unit tests (btcd unit-cover)	17m 31s
run windows itest	32m 29s
run ubuntu itests (bitcoind, backend=bitcoind cover=1)	41m 15s
run unit tests (unit tags="kvdb_etcd")	19m 20s
run unit tests (unit tags="kvdb_postgres")	18m 57s
run ubuntu itests (bitcoind-notxindex, backend="bitcoind notxindex")	41m 18s
run unit tests (unit tags="kvdb_sqlite")	17m 2s
run ubuntu itests (bitcoind-rpcpolling, backend="bitcoind rpcpolling" cover=1)	42m 10s
run unit tests (btcd unit-race)	36m 31s
run ubuntu itests (bitcoind-etcd, backend=bitcoind dbbackend=etcd)	57m 48s
run unit tests (unit-module)	4m 36s
run ubuntu itests (bitcoind-postgres, backend=bitcoind dbbackend=postgres)	1h 13m 13s
run ubuntu itests (bitcoind-sqlite, backend=bitcoind dbbackend=sqlite)	44m 2s
run ubuntu itests (bitcoind-postgres-nativesql, backend=bitcoind dbbackend=postgres nativesql=true)	1h 16m 36s
run ubuntu itests (bitcoind-sqlite-nativesql, backend=bitcoind dbbackend=sqlite nativesql=true)	44m 47s
run ubuntu itests (neutrino, backend=neutrino cover=1)	39m 31s
finish	3s
	12h 34m 40s

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