chore: increased designed timeout by 1 minute (#110)

Fixes #108  🦕

I ran 418 times to repro this error but Instead I got DeadlineExceeded exception.
Then, on the second attempt, I ran 78 times to repro this error.

this error occurs very randomly, I am not sure if its some kind of backend timeout or throttling.

First attempt to fix this --> increasing timeout 
If this won't work, i will increase it to 4 min.
 If that doesn't work, I will raise this issue as P1.

videointelligence/samples/quickstart/quickstart.py

@@ -37,7 +37,7 @@ def run_quickstart():
     )
     print("\nProcessing video for label annotations:")
 
-    result = operation.result(timeout=120)
+    result = operation.result(timeout=180)
     print("\nFinished processing.")
 
     # first result is retrieved because a single video was processed