chore: fix concurrent CommitQuota transactions for unrelated users/orgs (#15261)

The failure condition being fixed is `w1` and `w2` could belong
to different users, organizations, and templates and still cause a
serializable failure if run concurrently. This is because the old query 
did a `seq scan` on the `workspace_builds` table. Since that is the 
table being updated, we really want to prevent that.

So before this would fail for any 2 workspaces. Now it only fails if
`w1` and `w2` are owned by the same user and organization.

coderd/database/dbauthz/setup_test.go

@@ -34,6 +34,7 @@ var errMatchAny = xerrors.New("match any error")
 var skipMethods = map[string]string{
 	"InTx":           "Not relevant",
 	"Ping":           "Not relevant",
+	"PGLocks":        "Not relevant",
 	"Wrappers":       "Not relevant",
 	"AcquireLock":    "Not relevant",
 	"TryAcquireLock": "Not relevant",