Remove unused (and wrong) toolchain fiel

tools/dds_ci/toolchain.py

     Get the default toolchain that should be used for dev and test based on the
     host platform.
     """
-    if distro.id() == 'alpine':
-        # Alpine Linux cannot use the full audit mode, as asan and ubsan do not
-        # work with musl
-        return paths.TOOLS_DIR / 'gcc-9-test.jsonc'
     if sys.platform == 'win32':
         return paths.TOOLS_DIR / 'msvc-audit.jsonc'
     if sys.platform == 'linux':

tools/gcc-9-test.jsonc

-{
-    "$schema": "../res/toolchain-schema.json",
-    "compiler_id": "gnu",
-    "c_compiler": "gcc-9",
-    "cxx_compiler": "g++-9",
-    "cxx_version": "c++17",
-    "warning_flags": [
-        "-Werror",
-    ],
-    "debug": true
-}