chore: update Renovate configuration (#2846)

- remove GitHub Actions regex (it's now supported out of the box)
- change browser Docker versioning to major to prevent auto-merge (the new image is not used in the workflow, so the screenshots should be tested and updated manually)

renovate.json

@@ -14,12 +14,6 @@
   },
   "ignorePaths": ["dockers/texcmp/"],
   "regexManagers": [
-    {
-      "fileMatch": ["^\\.github/workflows/[^/]+\\.ya?ml$"],
-      "matchStrings": ["uses: (?<depName>.*?)@(?<currentValue>.*?)\\s"],
-      "datasourceTemplate": "github-tags",
-      "versioningTemplate": "regex:^v(?<major>\\d+)$"
-    },
     {
       "fileMatch": [
         "^\\.github/workflows/screenshotter\\.yml$",
@@ -28,7 +22,7 @@
       "matchStrings": ["[-\"](?<browserTag>[a-z]+):(?<currentValue>[\\d.\\-]+)[\"\\s]"],
       "datasourceTemplate": "docker",
       "depNameTemplate": "selenium/standalone-{{browserTag}}",
-      "versioningTemplate": "regex:^3\\.141\\.59-(?<patch>\\d+)$"
+      "versioningTemplate": "regex:^3\\.141\\.59-(?<major>\\d+)$"
     }, {
       "fileMatch": ["^\\.flowconfig$"],
       "matchStrings": ["\\[version\\]\\s*(?<currentValue>.*?)\\s"],