[packages] Set parallelizable to NO to reduce test flakiness in packages project tests (flutter#6471)

fixes flutter#146358

- [] I updated `pubspec.yaml` with an appropriate new version according to the [pub versioning philosophy], or this PR is [exempt from version changes].

Author: LouiseHsu

packages/google_sign_in/google_sign_in_ios/example/macos/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme

@@ -39,7 +39,7 @@
       <Testables>
          <TestableReference
             skipped = "NO"
-            parallelizable = "YES">
+            parallelizable = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "331C80D4294CF70F00263BE5"

packages/pointer_interceptor/pointer_interceptor_ios/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme

@@ -39,7 +39,7 @@
       <Testables>
          <TestableReference
             skipped = "NO"
-            parallelizable = "YES">
+            parallelizable = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "331C8080294A63A400263BE5"
@@ -50,7 +50,7 @@
          </TestableReference>
          <TestableReference
             skipped = "NO"
-            parallelizable = "YES">
+            parallelizable = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "F21CDF8F2B056DB70017C279"

packages/video_player/video_player/example/macos/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme

@@ -39,7 +39,7 @@
       <Testables>
          <TestableReference
             skipped = "NO"
-            parallelizable = "YES">
+            parallelizable = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "331C80D4294CF70F00263BE5"
@@ -50,7 +50,7 @@
          </TestableReference>
          <TestableReference
             skipped = "NO"
-            parallelizable = "YES">
+            parallelizable = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "33683FE32ABCABBC007305E4"

packages/video_player/video_player_avfoundation/example/macos/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme

@@ -39,7 +39,7 @@
       <Testables>
          <TestableReference
             skipped = "NO"
-            parallelizable = "YES">
+            parallelizable = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "331C80D4294CF70F00263BE5"
@@ -50,7 +50,7 @@
          </TestableReference>
          <TestableReference
             skipped = "NO"
-            parallelizable = "YES">
+            parallelizable = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "33683FE32ABCABBC007305E4"