Remove references to testbed pipeline from tests

Reference to undesired set of files wanted in general tests removed.

Tests/Scripts/Editor/Tests_Editor.asmdef

         "com.unity.render-pipelines.high-defintion.Editor",
         "com.unity.render-pipelines.lightweight.Editor",
         "GraphicTests",
-        "com.unity.render-pipelines.testbed-pipelines",
         "com.unity.postprocessing.Runtime",
         "com.unity.render-pipelines.core.IncludePaths",
         "com.unity.render-pipelines.core.Runtime",

Tests/Scripts/Tests.asmdef

         "com.unity.render-pipelines.core.IncludePaths",
         "com.unity.render-pipelines.core.Runtime",
         "com.unity.render-pipelines.high-definition.Runtime",
-        "com.unity.render-pipelines.lightweight.Runtime",
-        "com.unity.render-pipelines.testbed-pipelines"
+        "com.unity.render-pipelines.lightweight.Runtime"
     ],
     "optionalUnityReferences": [
         "TestAssemblies"