chore: Remove unused code from Timers

These were highlighted in the Android Studio diagnostics view.

IsScheduled() is never used because when looking up an ID in the timer
map, we always need the iterator later on.

The dispose field is never accessed.

Author: ptomato

test-app/runtime/src/main/cpp/Timers.h

@@ -40,7 +40,6 @@ namespace tns {
             args_.reset();
             isolate_ = nullptr;
             queued_ = false;
-            disposed = true;
         }
 
         int nestingLevel_ = 0;
@@ -59,7 +58,6 @@ namespace tns {
         double dueTime_ = -1;
         double startTime_ = -1;
         int id_;
-        bool disposed = false;
     };
 
     struct TimerReference {
@@ -110,11 +108,6 @@ namespace tns {
 
         void removeTask(const int &taskId);
 
-        inline bool IsScheduled(const int &id) {
-            auto it = timerMap_.find(id);
-            return it != timerMap_.end();
-        }
-
         v8::Isolate *isolate_ = nullptr;
         ALooper *looper_;
         int currentTimerId = 0;