[CFE] Mark two incremental tests slow (2nd try)
[CFE] Mark two incremental tests slow (2nd try)

The tests incremental_dart2js_test and incremental_compiler_leak_test
- taking ~1 minute each locally - often times out at 4 minutes (after
almost being done) on the bots. This CL gives them a little more time
hopefully allowing them to finish.

Fixes https://github.com/dart-lang/sdk/issues/43000

Note that this is the 2nd try as the first try accidentially had the
extension (.dart) in the status file so they did not apply.

Change-Id: I6bad5e96f247a65ec795b238308cc570454d3090
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/159247
Reviewed-by: Jens Johansen <05223a3c6bdf76af6f84755eae231abeebcf4530@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk