Update link format in next.md

Author: sylvestre

next.md

@@ -1,5 +1,5 @@
 This file documents the pending improvements or regression:
 
-* github.com/uutils/coreutils/pull/9063
+* https://github.com/uutils/coreutils/pull/9063
 * https://github.com/uutils/coreutils/issues/5705
 * https://github.com/uutils/coreutils/pull/9016 - merged but not yet reflected in test results