string-util: fix typo

Follow-up for 87b7d9b6ff.

src/fundamental/string-util-fundamental.c

@@ -82,7 +82,7 @@ static bool is_valid_version_char(sd_char a) {
 int strverscmp_improved(const sd_char *a, const sd_char *b) {
         /* This function is similar to strverscmp(3), but it treats '-' and '.' as separators.
          *
-         * The logic is based on rpm's rpmvercmp(), but unlike rpmvercmp(), it distiguishes e.g.
+         * The logic is based on rpm's rpmvercmp(), but unlike rpmvercmp(), it distinguishes e.g.
          * '123a' and '123.a', with '123a' being newer.
          *
          * It allows direct comparison of strings which contain both a version and a release; e.g.