docs: remove unused include from example in math/base/special/gamma/README.md

PR-URL: #2677

Signed-off-by: GUNJ JOSHI <[email protected]>
Reviewed-by: Philipp Burckhardt <[email protected]>

Author: gunjjoshi

lib/node_modules/@stdlib/math/base/special/gamma/README.md

@@ -187,7 +187,6 @@ double stdlib_base_gamma( const double x );
 
 ```c
 #include "stdlib/math/base/special/gamma.h"
-#include <stdlib.h>
 #include <stdio.h>
 
 int main( void ) {