test: assert on user id, not entire user (#23632)

User struct has "LastSeen" field which can change during the test


Replaces https://github.com/coder/coder/pull/23622

coderd/users_test.go

@@ -1714,7 +1714,7 @@ func TestGetUser(t *testing.T) {
 
 		user, err := client.User(ctx, exp.Username)
 		require.NoError(t, err)
-		require.Equal(t, exp, user)
+		require.Equal(t, exp.ID, user.ID)
 	})
 }