emscripten: remove no longer relevant comment

This was fixed in Emscripten 1.39.16, see:
d4fabf3da4

mesonbuild/compilers/detect.py

@@ -365,8 +365,7 @@ def _detect_c_or_cpp_compiler(env: 'Environment', lang: str, for_machine: Machin
 
             # emcc requires a file input in order to pass arguments to the
             # linker. It'll exit with an error code, but still print the
-            # linker version. Old emcc versions ignore -Wl,--version completely,
-            # however. We'll report "unknown version" in that case.
+            # linker version.
             with tempfile.NamedTemporaryFile(suffix='.c') as f:
                 cmd = compiler + [cls.LINKER_PREFIX + "--version", f.name]
                 _, o, _ = Popen_safe(cmd)