Use GitLab as data source for libtiff

Co-authored-by: Andrew Murray <3112309+radarhere@users.noreply.github.com>

Author: hugovk

.github/renovate.json

@@ -94,8 +94,8 @@
             "managerFilePatterns": ["/^\\.github/dependencies\\.json$/"],
             "matchStrings": ["\"tiff\":\\s*\"(?<currentValue>\\d+[^\"]*?)\""],
             "depNameTemplate": "tiff",
-            "packageNameTemplate": "libsdl-org/libtiff",
-            "datasourceTemplate": "github-tags",
+            "packageNameTemplate": "libtiff/libtiff",
+            "datasourceTemplate": "gitlab-tags",
             "extractVersionTemplate": "^v(?<version>.+)$"
         },
         {