ci: Disable iOS tests paralellization (#5086)

Author: itaybre

packages/core/RNSentryCocoaTester/RNSentryCocoaTester.xcodeproj/xcshareddata/xcschemes/RNSentryCocoaTester.xcscheme

@@ -30,7 +30,7 @@
       <Testables>
          <TestableReference
             skipped = "NO"
-            parallelizable = "YES">
+            parallelizable = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "3360898C29524164007C7730"