refactor: . Simplify an if statement, to finish reducing of complexity

SonarCloud pointed out that in obsidian-tasks-group#3003 I had increased the complexity in
Task.identicalTo() from 15 to 16.

By this change, and extracting Task.recurrenceIdenticalTo() it should have dropped
to below 15 now.

src/Task/Task.ts

@@ -868,11 +868,7 @@ export class Task extends ListItem {
  return false;
  }
 
- if (!this.file.rawFrontmatterIdenticalTo(other.file)) {
- return false;
- }
-
- return true;
+ return this.file.rawFrontmatterIdenticalTo(other.file);
  }
 
  private recurrenceIdenticalTo(other: Task) {