use hardcoded gitea url and main branch for pr creation

.gitea/workflows/helium-update.yml

@@ -96,7 +96,7 @@ jobs:
         run: |
           set -euo pipefail
 
-          api="${GITHUB_SERVER_URL}/api/v1/repos/${GITHUB_REPOSITORY}"
+          api="https://gitea.unrail.xyz/api/v1/repos/thomas/nixos-config"
           branch="bot/helium-${{ steps.update.outputs.version }}"
 
           # Skip if PR for this branch already exists
@@ -118,7 +118,7 @@ jobs:
           {
             \"title\": \"update helium to ${{ steps.update.outputs.version }}\",
             \"head\": \"${branch}\",
-            \"base\": \"${GITHUB_REF_NAME}\",
+            \"base\": \"main\",
             \"body\": \"automated update of helium appimage version and hash\"
           }
           JSON