Updated the events for workflows

Removed pull_request event which might be triggering the workflow
instead of pull_request_target. This could fix this issue but might
raise some security concerns.

Author: iamwatchdogs

.github/workflows/auto-assigner.yml

@@ -1,8 +1,6 @@
 name: Auto Assign
 
 on:
-  pull_request:
-    types: [opened, ready_for_review]
   pull_request_target:
     types: [opened, ready_for_review]
   issues:

.github/workflows/auto-commentor.yml

@@ -1,8 +1,6 @@
 name: Auto-commenter
 
 on:
-  pull_request:
-    types: [opened, closed]
   pull_request_target:
     types: [opened, closed]
 

.github/workflows/auto-labeler.yml

@@ -1,8 +1,6 @@
 name: hacktoberfest-labeler
 
 on:
-  pull_request:
-    types: [opened, reopened, closed]
   pull_request_target:
     types: [opened, reopened, closed]