treewide: fix a few typos in NEWS, docs and comments

src/basic/macro.h

@@ -418,7 +418,7 @@ typedef struct {
 
 assert_cc(sizeof(dummy_t) == 0);
 
-/* A little helper for subtracting 1 off a pointer in a safe UB-free way. This is intended to be used for for
+/* A little helper for subtracting 1 off a pointer in a safe UB-free way. This is intended to be used for
  * loops that count down from a high pointer until some base. A naive loop would implement this like this:
  *
  * for (p = end-1; p >= base; p--) …

src/basic/unit-file.c

@@ -329,7 +329,7 @@ int unit_file_resolve_symlink(
 
         assert(path_is_absolute(simplified));
 
-        /* Check if the symlink remain inside of of our search path.
+        /* Check if the symlink remain inside of our search path.
          * If yes, it is an alias. Verify that it is valid.
          *
          * If no, then this is a linked unit file or mask, and we don't care about the target name