Revert file rename from T59773 fix

Mixing file rename with other changes should be avoided.

Using 'module_py_api' convention here
is in keeping with imbuf, idprop, blf & bmesh.
No reason for gpu to have a different convention.

source/blender/python/gpu/gpu_py.h

@@ -1,34 +0,0 @@
-/*
- * ***** BEGIN GPL LICENSE BLOCK *****
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
- *
- * ***** END GPL LICENSE BLOCK *****
- */
-
-/** \file blender/python/gpu/gpu_py_api.h
- *  \ingroup bpygpu
- */
-
-#ifndef __GPU_PY_H__
-#define __GPU_PY_H__
-
-bool bpygpu_is_initialized(void);
-
-int bpygpu_ParsePrimType(PyObject *o, void *p);
-
-PyObject *BPyInit_gpu(void);
-
-#endif  /* __GPU_PY_H__ */