mesa: Remove the key parameter from the _mesa_HashWalk callback

_mesa_HashWalkLocked too.  After the previous couple commits, there are
no users.  This eliminates a lot of unused parameter warnings.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7171>

src/mesa/main/shared.c

@@ -226,7 +226,7 @@ delete_bufferobj_cb(GLuint id, void *data, void *userData)
  * to avoid memory access error.
  */
 static void
-free_shader_program_data_cb(GLuint id, void *data, void *userData)
+free_shader_program_data_cb(void *data, void *userData)
 {
    struct gl_context *ctx = (struct gl_context *) userData;
    struct gl_shader_program *shProg = (struct gl_shader_program *) data;