test: fix capitalized-comments lint in transform callback null test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: galaxy4276

test/parallel/test-stream-transform-callback-null.js

@@ -9,7 +9,7 @@ const { Transform } = require('stream');
 // side. Refs: https://github.com/nodejs/node/issues/62769
 
 {
-  // callback(null, null) should end the readable side of the transform stream.
+  // Calling callback(null, null) should end the readable side of the transform stream.
   const t = new Transform({
     transform(chunk, encoding, callback) {
       callback(null, null);
@@ -18,7 +18,7 @@ const { Transform } = require('stream');
 
   t.on('end', common.mustCall());
   t.on('data', (chunk) => {
-    // null sentinel should not appear as a data chunk
+    // Null sentinel should not appear as a data chunk.
     assert.fail('unexpected data event');
   });