[ci] Move Wasm test shards out of bringup. (flutter#8572)

This PR moves the new Wasm shards out of bringup, so they become part of the normal testing flow.

Here's some information about the last ~90 builds in the staging builder:

* Unit tests, master channel
  * [Shard 1](https://ci.chromium.org/ui/p/flutter/builders/staging/Linux_web%20web_dart_unit_test_wasm_shard_1%20master?limit=200)
  * [Shard 2](https://ci.chromium.org/ui/p/flutter/builders/staging/Linux_web%20web_dart_unit_test_wasm_shard_2%20master?limit=200)
* Integration tests, master channel 
  * [Shard 1](https://ci.chromium.org/ui/p/flutter/builders/staging/Linux_web%20web_platform_tests_wasm_shard_1%20master?limit=200)
  * [Shard 2](https://ci.chromium.org/ui/p/flutter/builders/staging/Linux_web%20web_platform_tests_wasm_shard_2%20master?limit=200)
  * [Shard 3](https://ci.chromium.org/ui/p/flutter/builders/staging/Linux_web%20web_platform_tests_wasm_shard_3%20master?limit=200)

## Issues

* Continuation of flutter#8111
* Completes flutter/flutter#151664
* Closes flutter/flutter#127730

Author: ditman

.ci.yaml

@@ -247,7 +247,6 @@ targets:
 
   # Wasm unit tests in master
   - name: Linux_web web_dart_unit_test_wasm_shard_1 master
-    bringup: true
     recipe: packages/packages
     timeout: 60
     properties:
@@ -263,7 +262,6 @@ targets:
         }
 
   - name: Linux_web web_dart_unit_test_wasm_shard_2 master
-    bringup: true
     recipe: packages/packages
     timeout: 60
     properties:
@@ -923,7 +921,6 @@ targets:
 
   # Wasm integration tests in master
   - name: Linux_web web_platform_tests_wasm_shard_1 master
-    bringup: true
     recipe: packages/packages
     timeout: 60
     properties:
@@ -938,7 +935,6 @@ targets:
         }
 
   - name: Linux_web web_platform_tests_wasm_shard_2 master
-    bringup: true
     recipe: packages/packages
     timeout: 60
     properties:
@@ -953,7 +949,6 @@ targets:
         }
 
   - name: Linux_web web_platform_tests_wasm_shard_3 master
-    bringup: true
     recipe: packages/packages
     timeout: 60
     properties: