[#491] Remove gcc test coverage report from badges in README.md

Author: mikir

README.md

@@ -5,7 +5,6 @@
 [![](https://github.com/ndsev/zserio/actions/workflows/build_linux.yml/badge.svg)](https://github.com/ndsev/zserio/actions/workflows/build_linux.yml)
 [![](https://github.com/ndsev/zserio/actions/workflows/build_windows.yml/badge.svg)](https://github.com/ndsev/zserio/actions/workflows/build_windows.yml)
 [![](https://img.shields.io/endpoint?url=https://zserio.org/doc/runtime/latest/cpp/coverage/clang/coverage_github_badge.json)](https://zserio.org/doc/runtime/latest/cpp/coverage/clang)
-[![](https://img.shields.io/endpoint?url=https://zserio.org/doc/runtime/latest/cpp/coverage/gcc/coverage_github_badge.json)](https://zserio.org/doc/runtime/latest/cpp/coverage/gcc)
 [![](https://img.shields.io/endpoint?url=https://zserio.org/doc/runtime/latest/java/coverage/coverage_github_badge.json)](https://zserio.org/doc/runtime/latest/java/coverage)
 [![](https://img.shields.io/endpoint?url=https://zserio.org/doc/runtime/latest/python/coverage/coverage_github_badge.json)](https://zserio.org/doc/runtime/latest/python/coverage)
 [![](https://img.shields.io/github/release-date/ndsev/zserio)](https://github.com/ndsev/zserio/releases/latest)

compiler/extensions/cpp/runtime/src/zserio/MainPage.dox

@@ -8,9 +8,5 @@
  * - Serialization (`SerializeUtil.h` module)
  * - Debug string output (`DebugStringUtil.h` module)
  *
- * Test coverage report of this library is available for <a href="coverage/gcc/index.html">gcc</a> and for
- * <a href="coverage/clang/index.html">clang</a>. Please note that <a href="coverage/gcc/index.html">gcc</a>
- * coverage report has many uncovered branches because of
- * <a href="https://gcovr.com/en/stable/faq.html#why-does-c-code-have-so-many-uncovered-branches">
- * different measurement approach</a>.
+ * <a href="coverage/clang/index.html">Test coverage report</a> of this library is available as well.
  */