👷 Remove clang-14-libstdc++ from build matrix

There is a bug in clang-14 consteval handling which interacts poorly with
libstdc++.

It manifests with the error: `call to consteval function
'std::chrono::hh_mm_ss::_S_fractional_width' is not a constant expression` when
compiling anything including `<chrono>`.

Author: elbeno

.github/workflows/unit_tests.yml

@@ -94,6 +94,9 @@ jobs:
             version: 15
           - compiler: gcc
             version: 14
+          - compiler: clang
+            version: 14
+            stdlib: libstdc++
           - compiler: clang
             version: 13
           - compiler: clang