[httpclient] Update usage help for `-3` option
@@ -452,7 +452,8 @@ static void usage(const char *progname)
"Usage: %s [options] <url>\n"
"Options:\n"
" -2 <ratio> HTTP/2 ratio (between 0 and 100)\n"
- " -3 HTTP/3-only mode\n"
+ " -3 <ratio> HTTP/3 ratio (between 0 and 100)\n"
+ " `ratio` can be omitted, implies `-3 100`\n"
" -b <size> size of request body (in bytes; default: 0)\n"
" -C <concurrency>\n"
" sets the number of requests run at once (default: 1)\n"
