test: adjust CLI flags test to ignore blank lines in doc

PR-URL: #40403
Backport-PR-URL: #40530
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

test/parallel/test-process-env-allowed-flags-are-documented.js

@@ -15,7 +15,9 @@ const parseSection = (text, startMarker, endMarker) => {
   const match = text.match(regExp);
   assert(match,
          `Unable to locate text between '${startMarker}' and '${endMarker}'.`);
-  return match[1].split(/\r?\n/);
+  return match[1]
+         .split(/\r?\n/)
+         .filter((val) => val.trim() !== '');
 };
 
 const nodeOptionsLines = parseSection(cliText,
@@ -24,6 +26,7 @@ const nodeOptionsLines = parseSection(cliText,
 const v8OptionsLines = parseSection(cliText,
                                     '<!-- node-options-v8 start -->',
                                     '<!-- node-options-v8 end -->');
+
 // Check the options are documented in alphabetical order.
 assert.deepStrictEqual(nodeOptionsLines, [...nodeOptionsLines].sort());
 assert.deepStrictEqual(v8OptionsLines, [...v8OptionsLines].sort());