Change trigger rules to activate paths filter

Previously there were two trigger conditions (PRs and pushes to main).
With the change all pushes (to PR branches or main) trigger it,
and the `paths:` filter applies every time.

This is a follow-up to #5364.

.github/workflows/arviz_compat.yml

@@ -1,9 +1,7 @@
 name: arviz-compatibility
 
 on:
-  pull_request:
   push:
-    branches: [main]
     paths:
       - ".github/workflows/*"
       - "pymc/**"

.github/workflows/jaxtests.yml

@@ -1,9 +1,7 @@
 name: jax-sampling
 
 on:
-  pull_request:
   push:
-    branches: [main]
     paths:
       - ".github/workflows/*"
       - "pymc/**"

.github/workflows/pre-commit.yml

@@ -1,9 +1,7 @@
 name: pre-commit
 
 on:
-  pull_request:
   push:
-    branches: [main]
 
 jobs:
   pre-commit:

.github/workflows/pytest.yml

@@ -1,9 +1,7 @@
 name: pytest
 
 on:
-  pull_request:
   push:
-    branches: [main]
     paths:
       - ".github/workflows/*"
       - "pymc/**"