chore(ci): fix WHMCS Marketplace login env var name

https://github.com/centralnicgroup-opensource/rtldev-middleware-semantic-release-whmcs#environment-variables

Author: scop

.github/workflows/release.yaml

@@ -30,7 +30,7 @@ jobs:
       - name: Release
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          WHMCSMP_USERNAME: ${{ secrets.WHMCSMP_USERNAME }}
+          WHMCSMP_LOGIN: ${{ secrets.WHMCSMP_LOGIN }}
           WHMCSMP_PASSWORD: ${{ secrets.WHMCSMP_PASSWORD }}
           WHMCSMP_PRODUCTID: "7770"
           WHMCSMP_MINVERSION: "7.0"