chore(deps): switch dependabot to monthly schedule

Author: kYaRick

.github/dependabot.yml

@@ -3,8 +3,7 @@ updates:
   - package-ecosystem: nuget
     directory: "/"
     schedule:
-      interval: weekly
-      day: monday
+      interval: monthly
       time: "06:00"
       timezone: Europe/Kyiv
     open-pull-requests-limit: 1
@@ -22,8 +21,7 @@ updates:
   - package-ecosystem: github-actions
     directory: "/"
     schedule:
-      interval: weekly
-      day: monday
+      interval: monthly
       time: "06:00"
       timezone: Europe/Kyiv
     open-pull-requests-limit: 1