[openmp] Remove extra ';' outside of function

Fixes:
```
[4038/11058] Building CXX object projects/openmp/libomptarget/src/CMakeFiles/omptarget.dir/OpenMP/InteropAPI.cpp.o
/home/aganea/llvm-project/openmp/libomptarget/src/OpenMP/InteropAPI.cpp:202:2: warning: extra ';' outside of a function is incompatible with C++98 [-Wc++98-compat-extra-semi]
};
 ^
1 warning generated.
```

openmp/libomptarget/src/OpenMP/InteropAPI.cpp

@@ -199,7 +199,7 @@ static const char *copyErrorString(llvm::Error &&Err) {
   char *UsrMsg = reinterpret_cast<char *>(malloc(ErrMsg.size() + 1));
   strcpy(UsrMsg, ErrMsg.c_str());
   return UsrMsg;
-};
+}
 
 extern "C" {