benchmark: remove double word "then" in comments

PR-URL: #29823
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

benchmark/net/net-pipe.js

@@ -49,7 +49,7 @@ function main({ dur, len, type }) {
 
       setTimeout(() => {
         // Multiply by 2 since we're sending it first one way
-        // then then back again.
+        // then back again.
         const bytes = writer.received * 2;
         const gbits = (bytes * 8) / (1024 * 1024 * 1024);
         bench.end(gbits);

benchmark/net/tcp-raw-pipe.js

@@ -106,7 +106,7 @@ function main({ dur, len, type }) {
 
     setTimeout(() => {
       // Multiply by 2 since we're sending it first one way
-      // then then back again.
+      // then back again.
       bench.end(2 * (bytes * 8) / (1024 * 1024 * 1024));
       process.exit(0);
     }, dur * 1000);