doc: fix spacing issue in --build-snapshot help text

PR-URL: nodejs/node#44435
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Kohei Ueno <kohei.ueno119@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: LiviaMedeiros <livia@cirno.name>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

src/node_options.cc

@@ -750,7 +750,7 @@ PerProcessOptionsParser::PerProcessOptionsParser(
             kAllowedInEnvironment);
   AddOption("--build-snapshot",
             "Generate a snapshot blob when the process exits."
-            "Currently only supported in the node_mksnapshot binary.",
+            " Currently only supported in the node_mksnapshot binary.",
             &PerProcessOptions::build_snapshot,
             kDisallowedInEnvironment);