[clang-format] Fix namespace format when the name is followed by a macro

Example:
```
$ cat a.cpp
namespace my_namespace::yeah API_AVAILABLE(macos(10.15)) {
void test() {}
}

$ clang-format a.cpp
namespace my_namespace::yeah API_AVAILABLE(macos(10.15)) {
void test() {}
}// namespace my_namespace::yeahAPI_AVAILABLE(macos(10.15))
```
After:
```
$ clang-format a.cpp
namespace my_namespace::yeah API_AVAILABLE(macos(10.15)) {
void test() {}
}// namespace my_namespace::yeah
```

Reviewed By: MyDeveloperDay, owenpan, curdeius

Differential Revision: https://reviews.llvm.org/D121269