Update PR template for releases

Author: wahln

.github/PULL_REQUEST_TEMPLATE/release_checklist_pull_request.md

@@ -3,14 +3,14 @@ Version of new Release and Type (new major release, minor release, patch release
 
 ### Release Checklist
 
-- [ ] Version number changed in matRad_getVersion
-- [ ] Adapted Changelog.txt
+- [ ] Adapted Changelog.md
 - [ ] All required mex files compiled
 - [ ] Third Party libraries / scripts up to date
 - [ ] Standalone(s) generated and tested
 - [ ] Wiki adapted
 - [ ] Optional changes to README.md
 - [ ] Check license information
+- [ ] Version number changed in matRad_getVersion
 
 ### References
 Any references regarding new functionality etc.