don't run the CI twice

.github/workflows/test_challenge.yml

 name: Test Challenge
 
-on: [push, pull_request]
+on: push
 
 jobs:
   unit:

.github/workflows/test_challenge_fault.yml

 name: Test Challenge Fault
 
-on: [push, pull_request]
+on: push
 
 jobs:
   unit:

.github/workflows/test_challenge_simple.yml

 name: Test Challenge Simple
 
-on: [push, pull_request]
+on: push
 
 jobs:
   unit:

.github/workflows/test_contracts.yml

 name: Test Contracts
 
-on: [push, pull_request]
+on: push
 
 jobs:
   unit:

.github/workflows/test_minigeth.yml

 name: Test minigeth
 
-on: [push, pull_request]
+on: push
 
 jobs:
   unit:
@@ -24,4 +24,4 @@ jobs:
     - name: Test block 13284053 (deletion)
       run: minigeth/go-ethereum 13284053
     - name: Test block 13303075 (uncles)
-      run: minigeth/go-ethereum 13303075
+      run: minigeth/go-ethereum 13303075
\ No newline at end of file

.github/workflows/test_mipsevm.yml

 name: Test MIPS EVM
 
-on: [push, pull_request]
+on: push
 
 jobs:
   unit: