ci(renovate): Fix missing escape in renovate config

renovate.json

@@ -27,7 +27,7 @@
     {
       "fileMatch": ["Earthfile$"],
       "matchStrings": [
-          "FROM\\s+(?<depName>(?!\\+)[a-z0-9./-]+):?(?<currentValue>[a-z0-9-.]+)?@?(?<currentDigest>sha256:[a-f0-9]+)?"
+          "FROM\\s+(?<depName>(?!\\+)[a-z0-9.\\/-]+):?(?<currentValue>[a-z0-9-.]+)?@?(?<currentDigest>sha256:[a-f0-9]+)?"
       ],
       "datasourceTemplate": "docker",
       "versioningTemplate": "docker"