Fix grammar of changelog a bit for cpp mangle update

changelog/mangle_cpp.dd

@@ -4,7 +4,7 @@ The new syntax allows for keywords to be used for mangling
 and only changes the mangle of a symbol. It does not provide any
 feature resembling C++ namespaces. This allows users to structure
 their C++ in traditional D fashion, utilizing modules. The old syntax
-`extern(C++, foo)` would occupy the symbol `foo`. This would modules
+`extern(C++, foo)` would occupy the symbol `foo`. This meant modules
 couldn't use this name and match the C++ namespace.
 
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