[ci] Fix legacy Android task names (flutter#5191)

Uses a capital for the first letter of the task names for consistency with the other tasks (which affects sorting in the GitHub PR UI).

Part of flutter#130010

Author: stuartmorgan-g

.ci.yaml

@@ -541,7 +541,7 @@ targets:
           {"dependency": "android_virtual_device", "version": "33"}
         ]
 
-  - name: linux_android_legacy android_platform_tests_legacy_api_shard_1 master
+  - name: Linux_android_legacy android_platform_tests_legacy_api_shard_1 master
     recipe: packages/packages
     timeout: 60
     bringup: true # New target
@@ -551,7 +551,7 @@ targets:
       version_file: flutter_master.version
       package_sharding: "--shardIndex 0 --shardCount 6"
 
-  - name: linux_android_legacy android_platform_tests_legacy_api_shard_2 master
+  - name: Linux_android_legacy android_platform_tests_legacy_api_shard_2 master
     recipe: packages/packages
     timeout: 60
     bringup: true # New target
@@ -561,7 +561,7 @@ targets:
       version_file: flutter_master.version
       package_sharding: "--shardIndex 1 --shardCount 6"
 
-  - name: linux_android_legacy android_platform_tests_legacy_api_shard_3 master
+  - name: Linux_android_legacy android_platform_tests_legacy_api_shard_3 master
     recipe: packages/packages
     timeout: 60
     bringup: true # New target
@@ -571,7 +571,7 @@ targets:
       version_file: flutter_master.version
       package_sharding: "--shardIndex 2 --shardCount 6"
 
-  - name: linux_android_legacy android_platform_tests_legacy_api_shard_4 master
+  - name: Linux_android_legacy android_platform_tests_legacy_api_shard_4 master
     recipe: packages/packages
     timeout: 60
     bringup: true # New target
@@ -581,7 +581,7 @@ targets:
       version_file: flutter_master.version
       package_sharding: "--shardIndex 3 --shardCount 6"
 
-  - name: linux_android_legacy android_platform_tests_legacy_api_shard_5 master
+  - name: Linux_android_legacy android_platform_tests_legacy_api_shard_5 master
     recipe: packages/packages
     timeout: 60
     bringup: true # New target
@@ -591,7 +591,7 @@ targets:
       version_file: flutter_master.version
       package_sharding: "--shardIndex 4 --shardCount 6"
 
-  - name: linux_android_legacy android_platform_tests_legacy_api_shard_6 master
+  - name: Linux_android_legacy android_platform_tests_legacy_api_shard_6 master
     recipe: packages/packages
     timeout: 60
     bringup: true # New target