macOS GateKeeper Helper mentioned 4 times in readme.md

Repro steps:
1. Navigate to https://github.com/serhii-londar/open-source-mac-os-apps/blob/master/README.md
2. Use Ctrl+F / CMD+F and search for "macOS GateKeeper Helper"
Expected result:
- Only one match found
Actual result:
- Four matches found
Impact:
An issue slightly reduce readability and easiness of navigation through catalogue of links listed in readme.md