only run github CI on latest commit of branch/PR (#20361)

based on [this](https://stackoverflow.com/a/72408109/10633874)

.github/workflows/ci_docs.yml

@@ -30,6 +30,10 @@ on:
       - '.github/workflows/ci_docs.yml'
       - 'koch.nim'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     strategy:

.github/workflows/ci_packages.yml

@@ -7,6 +7,10 @@ on:
       - 'version-1-6'
       - 'version-1-2'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     strategy: