Fix comment

Signed-off-by: Chengwei Yang <[email protected]>

gh-md-toc

@@ -9,12 +9,12 @@
 #  2. Discard rows where no substring 'user-content-' (github's markup):
 #       awk '/user-content-/ { ...
 #
-#  3.1 Get last number in each row like ' ... </span></a>sitemap.js</h1>'.
-#      It's a level of the current header (NF — number of fields):
-#       substr($NF, length($NF)-1, 1)
+#  3.1 Get last number in each row like ' ... </span></a>sitemap.js</h1'.
+#      It's a level of the current header:
+#       substr($0, length($0), 1)
 #
 #  3.2 Get level from 3.1 and insert corresponding number of spaces before '*':
-#       sprintf("%*s", substr($NF, length($NF)-1, 1)*2, " ")
+#       sprintf("%*s", substr($0, length($0), 1)*2, " ")
 #
 #  4. Find head's text and insert it inside "* [ ... ]":
 #       substr($0, match($0, /a>.*<\/h/)+2, RLENGTH-5)