git-compat-util.h: drop the PRIuMAX definition

Git's code base already seems to be using `PRIdMAX` without any such
fallback definition for quite a while (7545941 (json_writer: new
routines to create JSON data, 2018-07-13), to be precise, and the
first Git version to include that commit was v2.19.0).

Therefore it should be safe to drop the fallback definition for
`PRIuMAX` in `git-compat-util.h`.

This addresses gitgitgadget#399

Signed-off-by: Hariom Verma <[email protected]>

Author: harry-hov

git-compat-util.h

@@ -320,10 +320,6 @@ char *gitdirname(char *);
 #define PATH_MAX 4096
 #endif
 
-#ifndef PRIuMAX
-#define PRIuMAX "llu"
-#endif
-
 #ifndef SCNuMAX
 #define SCNuMAX PRIuMAX
 #endif