fix: alternative route of getting latest Gitea version

Use a code.forgejo.org mirror instead of the GitHub API to not be
subject to rate limiting.

upgrade/upgrade.sh

@@ -67,6 +67,11 @@ function migration_assert() {
 }
 
 function test_gitea_upgrades() {
+    local token="$1"
+    GITEA_AUTHORIZATION_HEADER="Authorization: token $token"
+
+    run dependencies
+
     local config=$UPGRADE_DIR/default-app.ini
     # The Forgejo target migration version must be 10.0 because it is the last supported.
     # https://forgejo.org/2024-12-gitea-compatibility/
@@ -104,5 +109,4 @@ function test_upgrades() {
 
     run test_successful_upgrades
     run test_forgejo_pprof
-    run test_gitea_upgrades
 }