Removed the vi format comments from the source

Vim users can use the [editorconfig plugin](https://github.com/editorconfig/editorconfig-vim) to automatically set tab spacing for the SDL coding style.

Fixes https://github.com/libsdl-org/SDL/issues/6903

src/thread/stdcpp/SDL_syscond.cpp

@@ -139,5 +139,3 @@ SDL_CondWaitTimeoutNS(SDL_cond *cond, SDL_mutex *mutex, Sint64 timeoutNS)
         return SDL_SetError("Unable to wait on a C++ condition variable: code=%d; %s", ex.code(), ex.what());
     }
 }
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/stdcpp/SDL_sysmutex.cpp

@@ -97,5 +97,3 @@ SDL_UnlockMutex(SDL_mutex *mutex) SDL_NO_THREAD_SAFETY_ANALYSIS /* clang doesn't
     mutex->cpp_mutex.unlock();
     return 0;
 }
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/stdcpp/SDL_sysmutex_c.h

@@ -26,5 +26,3 @@ struct SDL_mutex
 {
     std::recursive_mutex cpp_mutex;
 };
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/stdcpp/SDL_systhread.cpp

@@ -159,5 +159,3 @@ SDL_SYS_SetTLSData(SDL_TLSData *data)
 {
     return SDL_Generic_SetTLSData(data);
 }
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/stdcpp/SDL_systhread_c.h

@@ -22,5 +22,3 @@
 
 /* For a thread handle, use a void pointer to a std::thread */
 typedef void *SYS_ThreadHandle;
-
-/* vi: set ts=4 sw=4 expandtab: */