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/generic/SDL_syscond.c

@@ -217,5 +217,3 @@ int SDL_CondWaitTimeoutNS_generic(SDL_cond *_cond, SDL_mutex *mutex, Sint64 time
 
     return retval;
 }
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/generic/SDL_syscond_c.h

@@ -34,5 +34,3 @@ int SDL_CondWaitTimeoutNS_generic(SDL_cond *cond, SDL_mutex *mutex, Sint64 timeo
 #endif /* SDL_THREAD_GENERIC_COND_SUFFIX */
 
 #endif /* SDL_syscond_generic_h_ */
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/generic/SDL_sysmutex.c

@@ -159,5 +159,3 @@ int SDL_UnlockMutex(SDL_mutex *mutex) SDL_NO_THREAD_SAFETY_ANALYSIS /* clang doe
     return 0;
 #endif /* SDL_THREADS_DISABLED */
 }
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/generic/SDL_sysmutex_c.h

@@ -19,4 +19,3 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 #include "SDL_internal.h"
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/generic/SDL_syssem.c

@@ -175,5 +175,3 @@ int SDL_SemPost(SDL_sem *sem)
 }
 
 #endif /* SDL_THREADS_DISABLED */
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/generic/SDL_systhread.c

@@ -60,5 +60,3 @@ void SDL_SYS_DetachThread(SDL_Thread *thread)
 {
     return;
 }
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/generic/SDL_systhread_c.h

@@ -22,5 +22,3 @@
 
 /* Stub until we implement threads on this platform */
 typedef int SYS_ThreadHandle;
-
-/* vi: set ts=4 sw=4 expandtab: */

src/thread/generic/SDL_systls.c

@@ -32,5 +32,3 @@ int SDL_SYS_SetTLSData(SDL_TLSData *data)
 {
     return SDL_Generic_SetTLSData(data);
 }
-
-/* vi: set ts=4 sw=4 expandtab: */