fix(app, android): avoid API24-only APIs, fix Android < 7 crash from 11.3.0 (#5206)

Author: ifsnow

packages/app/android/src/main/java/io/invertase/firebase/common/TaskExecutorService.java

@@ -101,12 +101,13 @@ public String getExecutorName(boolean isTransactional, String identifier) {
 
   public void shutdown() {
     Set<String> existingExecutorNames = executors.keySet();
-    existingExecutorNames.removeIf((executorName) -> {
-      return executorName.startsWith(name) == false;
-    });
-    existingExecutorNames.forEach((executorName) -> {
-      removeExecutor(executorName);
-    });
+    for (String executorName : existingExecutorNames) {
+      if (executorName.startsWith(name) == false) {
+        existingExecutorNames.remove(executorName);
+      } else {
+        removeExecutor(executorName);  
+      }
+    }
   }
 
   public void removeExecutor(String executorName) {