fix(schemas): remove redundant patterns from date-time defs

The pre-defined date-time, unlike the full date-time format expected by GitVerison, requires `[zZ]|([-+]([zZ]|([01][0-9]|2[0-3]):[0-5][0-9]))`

Author: BinToss

schemas/5.12/GitVersion.configuration.json

@@ -386,7 +386,6 @@
     },
     "Nullable\u006012": {
       "format": "date-time",
-      "pattern": "\u0027yyyy-MM-ddTHH:mm:ss\u0027",
       "description": "Commits before this date will be ignored. Format: yyyy-MM-ddTHH:mm:ss.",
       "type": [
         "string",

schemas/6.0/GitVersion.configuration.json

@@ -331,7 +331,6 @@
     },
     "nullableOfDateTimeOffset": {
       "format": "date-time",
-      "pattern": "\u0027yyyy-MM-ddTHH:mm:ss\u0027",
       "description": "Commits before this date will be ignored. Format: yyyy-MM-ddTHH:mm:ss.",
       "type": [
         "string",