src: fix -Wimplicit-fallthrough warning

PR-URL: https://github.com/nodejs/node/pull/18205
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

src/node_i18n.cc

@@ -788,7 +788,8 @@ static int GetColumnWidth(UChar32 codepoint,
       if (ambiguous_as_full_width) {
         return 2;
       }
-      // Fall through if ambiguous_as_full_width if false.
+      // If ambiguous_as_full_width is false:
+      // Fall through
     case U_EA_NEUTRAL:
       if (u_hasBinaryProperty(codepoint, UCHAR_EMOJI_PRESENTATION)) {
         return 2;