Remove unneeded permissions of GitHub action that validates CITATION.cff

Author: abelsiqueira

.github/workflows/cffconvert.yml

@@ -5,13 +5,18 @@ on:
     paths:
       - CITATION.cff
 
+permissions:
+  contents: read
+
 jobs:
   validate:
     name: "validate"
     runs-on: ubuntu-latest
     steps:
       - name: Check out a copy of the repository
         uses: actions/checkout@v2
+        with:
+          persist-credentials: false
 
       - name: Check whether the citation metadata from CITATION.cff is valid
         uses: citation-file-format/[email protected]