Mark new_gallery__transition_perf as non-flaky (#114694)

These were marked flaky due to a timeout switching between items in the
Studies list at the top of the screen, which had snap-to-item scroll
physics.

The same flake also affected new_gallery_impeller__transition_perf which
was failing with the same flake, though was separately marked flaky due
to a separate (engine crash) flake documented in:
* flutter/flutter#112577
* flutter/flutter#112438

Leaving the latter marked flaky for the time being while that separate
issue is investigated.

Issue: flutter/flutter#114025

.ci.yaml

@@ -1995,7 +1995,6 @@ targets:
 
   - name: Linux_android new_gallery__transition_perf
     recipe: devicelab/devicelab_drone
-    bringup: true # Flaky: https://github.com/flutter/flutter/issues/114025
     presubmit: false
     timeout: 60
     properties: