feat: remove the days-before-stale option

BREAKING CHANGE:
The option days-before-stale was removed

__tests__/constants/default-processor-options.ts

@@ -6,9 +6,8 @@ export const DefaultProcessorOptions: IIssuesProcessorOptions = Object.freeze({
   stalePrMessage: 'This PR is stale',
   closeIssueMessage: 'This issue is being closed',
   closePrMessage: 'This PR is being closed',
-  daysBeforeStale: 1,
-  daysBeforeIssueStale: NaN,
-  daysBeforePrStale: NaN,
+  daysBeforeIssueStale: 1,
+  daysBeforePrStale: 1,
   daysBeforeIssueClose: 30,
   daysBeforePrClose: 30,
   staleIssueLabel: 'Stale',