Run GitHub actions only on PR

With so many github actions (>60) we cannot afford to run on every push

Author: pepeiborra

.github/workflows/nix.yml

@@ -1,6 +1,6 @@
 name: Nix
 
-on: [push, pull_request]
+on: [pull_request]
 jobs:
   nix:
     runs-on: ${{ matrix.os }}

.github/workflows/test.yml

@@ -1,6 +1,6 @@
 name: Testing
 
-on: [push, pull_request]
+on: [pull_request]
 jobs:
   test:
     runs-on: ${{ matrix.os }}