README: remove gitlab badges [skip-ci]

gitlab ci is no longer used

README.md

@@ -1,9 +1,7 @@
 [![Gitter](https://badges.gitter.im/libspng/community.svg)](https://gitter.im/libspng/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 [![Financial Contributors on Open Collective](https://opencollective.com/libspng/all/badge.svg?label=financial+contributors)](https://opencollective.com/libspng)
-[![GitLab CI](https://gitlab.com/randy408/libspng-ci/badges/master/pipeline.svg)](https://gitlab.com/randy408/libspng-ci/pipelines/latest)
 [![Fuzzing Status](https://oss-fuzz-build-logs.storage.googleapis.com/badges/libspng.svg)](https://oss-fuzz-build-logs.storage.googleapis.com/index.html#libspng)
 [![Coverity](https://scan.coverity.com/projects/15336/badge.svg)](https://scan.coverity.com/projects/randy408-libspng)
-[![coverage](https://gitlab.com/randy408/libspng-ci/badges/master/coverage.svg)](https://gitlab.com/randy408/libspng-ci/-/graphs/master/charts)
 [![tag](https://img.shields.io/github/tag-date/randy408/libspng.svg)](https://libspng.org/download)
 
 # libspng