⬆️: migrate renovate config (#420)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: renovate[bot] <renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/renovate.json

@@ -8,7 +8,7 @@
   "customManagers": [
     {
       "customType": "regex",
-      "fileMatch": ["/Dockerfile$", "/build.yaml$"],
+      "managerFilePatterns": ["//Dockerfile$/", "//build.yaml$/"],
       "matchStringsStrategy": "any",
       "matchStrings": [
         "ARG BUILD_FROM=(?<depName>.*?):(?<currentValue>.*?)\\s+",
@@ -18,7 +18,7 @@
     },
     {
       "customType": "regex",
-      "fileMatch": ["/Dockerfile$"],
+      "managerFilePatterns": ["//Dockerfile$/"],
       "matchStringsStrategy": "any",
       "matchStrings": [
         "\\s\\s(?<package>[a-z0-9][a-z0-9-_]+)=(?<currentValue>[a-z0-9-_.]+)\\s+"
@@ -29,7 +29,7 @@
     },
     {
       "customType": "regex",
-      "fileMatch": ["/Dockerfile$"],
+      "managerFilePatterns": ["//Dockerfile$/"],
       "matchStrings": [
         "ARG BOOKSTACK_VERSION=[\"']?(?<currentValue>.+?)[\"']?\\s+"
       ],