ci: rename secrets.GITHUB_TOKEN to github.token for clarity

It becomes clear that this isn't a repo configured secret, but the
token made available by github's system.

Author: consideRatio

.github/workflows/tests.yaml

@@ -37,7 +37,7 @@ jobs:
     env:
       # Use TOKEN_READONLY if available (pushed branches), otherwise use GITHUB_TOKEN (PRs)
       # TOKEN_READONLY is a PAT for @choldgraf that only has read-access to this repo but isn't available in PRs.
-      GITHUB_ACCESS_TOKEN: "${{ secrets.TOKEN_READONLY || secrets.GITHUB_TOKEN }}"
+      GITHUB_ACCESS_TOKEN: "${{ secrets.TOKEN_READONLY || github.token }}"
     strategy:
       matrix:
         include: