[ci] Enable legacy Android emulator tests (#5190)

Enables the new legacy emulator targets.

Fixes flutter/flutter#130010

.ci.yaml

@@ -551,7 +551,6 @@ targets:
   - name: Linux_android_legacy android_platform_tests_legacy_api_shard_1 master
     recipe: packages/packages
     timeout: 60
-    bringup: true # New target
     properties:
       target_file: android_legacy_emulator_tests.yaml
       channel: master
@@ -561,7 +560,6 @@ targets:
   - name: Linux_android_legacy android_platform_tests_legacy_api_shard_2 master
     recipe: packages/packages
     timeout: 60
-    bringup: true # New target
     properties:
       target_file: android_legacy_emulator_tests.yaml
       channel: master
@@ -571,7 +569,6 @@ targets:
   - name: Linux_android_legacy android_platform_tests_legacy_api_shard_3 master
     recipe: packages/packages
     timeout: 60
-    bringup: true # New target
     properties:
       target_file: android_legacy_emulator_tests.yaml
       channel: master
@@ -581,7 +578,6 @@ targets:
   - name: Linux_android_legacy android_platform_tests_legacy_api_shard_4 master
     recipe: packages/packages
     timeout: 60
-    bringup: true # New target
     properties:
       target_file: android_legacy_emulator_tests.yaml
       channel: master
@@ -591,7 +587,6 @@ targets:
   - name: Linux_android_legacy android_platform_tests_legacy_api_shard_5 master
     recipe: packages/packages
     timeout: 60
-    bringup: true # New target
     properties:
       target_file: android_legacy_emulator_tests.yaml
       channel: master
@@ -601,7 +596,6 @@ targets:
   - name: Linux_android_legacy android_platform_tests_legacy_api_shard_6 master
     recipe: packages/packages
     timeout: 60
-    bringup: true # New target
     properties:
       target_file: android_legacy_emulator_tests.yaml
       channel: master