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/pthread/SDL_syscond.c

@@ -142,5 +142,3 @@ tryagain:
     }
     return retval;
 }
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/pthread/SDL_sysmutex.c

@@ -185,5 +185,3 @@ int SDL_UnlockMutex(SDL_mutex *mutex) SDL_NO_THREAD_SAFETY_ANALYSIS /* clang doe
 
     return 0;
 }
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/pthread/SDL_sysmutex_c.h

@@ -29,4 +29,3 @@ struct SDL_mutex
 };
 
 #endif /* SDL_mutex_c_h_ */
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/pthread/SDL_syssem.c

@@ -182,4 +182,3 @@ int SDL_SemPost(SDL_sem *sem)
 }
 
 #endif /* __MACOS__ */
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/pthread/SDL_systhread.c

@@ -282,5 +282,3 @@ void SDL_SYS_DetachThread(SDL_Thread *thread)
 {
     pthread_detach(thread->handle);
 }
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/pthread/SDL_systhread_c.h

@@ -23,5 +23,3 @@
 #include <pthread.h>
 
 typedef pthread_t SYS_ThreadHandle;
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/pthread/SDL_systls.c

@@ -63,5 +63,3 @@ int SDL_SYS_SetTLSData(SDL_TLSData *data)
     }
     return 0;
 }
-
-/* vi: set ts=4 sw=4 expandtab: */