chore: remove unnecessary loop variable captures (#22180)

Since Go 1.22, the loop variable capture issue is resolved. Variables
declared by for loops are now per-iteration rather than per-loop, making
the 'v := v' pattern unnecessary.

coderd/agentapi/subagent_test.go

@@ -1320,7 +1320,6 @@ func TestSubAgentAPI(t *testing.T) {
 		}
 
 		for _, tc := range tests {
-			tc := tc
 			t.Run(tc.name, func(t *testing.T) {
 				t.Parallel()