fix(renovate): use fileMatch instead of managerFilePatterns

managerFilePatterns is known to cause Renovate to silently fail to
match files (see renovatebot/renovate#36287). Switch to fileMatch
which works correctly in all Renovate versions.

renovate.json

@@ -4,7 +4,7 @@
     {
       "customType": "regex",
       "description": "Detect SABnzbd release version pin",
-      "managerFilePatterns": ["/Dockerfile/"],
+      "fileMatch": ["^Dockerfile$"],
       "matchStrings": ["SABNZBD_VERSION=(?<currentValue>[0-9.]+)"],
       "depNameTemplate": "sabnzbd/sabnzbd",
       "datasourceTemplate": "github-releases"
@@ -12,7 +12,7 @@
     {
       "customType": "regex",
       "description": "Detect Tini release version pin",
-      "managerFilePatterns": ["/Dockerfile/"],
+      "fileMatch": ["^Dockerfile$"],
       "matchStrings": ["\"TINI_VERSION\"\\s+\"v?(?<currentValue>[0-9.]+)\""],
       "depNameTemplate": "krallin/tini",
       "datasourceTemplate": "github-releases"
@@ -20,10 +20,10 @@
     {
       "customType": "regex",
       "description": "Detect par2cmdline release version pin",
-      "managerFilePatterns": ["/Dockerfile/"],
+      "fileMatch": ["^Dockerfile$"],
       "matchStrings": ["PAR2CMDLINE_VERSION=v?(?<currentValue>[0-9a-z.]+-mt\\d+)"],
       "depNameTemplate": "jkansanen/par2cmdline-mt",
       "datasourceTemplate": "github-tags"
     }
   ]
-}
+}