[chromedriver] Add missing comma that broke --help parsing

Bug: None
Change-Id: I9a0817a90270266a538062aaf4e322a86fa3ed6b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2422146Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809446}

chrome/test/chromedriver/server/chromedriver_server.cc

@@ -325,7 +325,7 @@ int main(int argc, char *argv[]) {
         "readable-timestamp",
             "add readable timestamps to log",
         "enable-chrome-logs",
-            "show logs from the browser (overrides other logging options)"
+            "show logs from the browser (overrides other logging options)",
 #if defined(OS_LINUX) && !defined(OS_CHROMEOS)
         "disable-dev-shm-usage",
             "do not use /dev/shm "