[ChromeDriver] Add shengfa@ to ChromeDriver OWNERS

Change-Id: I366350f45ee519bf1410fbe198d90b5f64814d7f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2372919
Auto-Submit: John Chen <johnchen@chromium.org>
Reviewed-by: Shengfa Lin <shengfa@google.com>
Commit-Queue: Shengfa Lin <shengfa@google.com>
Cr-Commit-Position: refs/heads/master@{#801144}

chrome/test/chromedriver/OWNERS

 # primary reviewer
+shengfa@google.com
+
+# secondary reviewer
 johnchen@chromium.org
 
 # COMPONENT: Test>WebDriver

third_party/webdriver/OWNERS

 # primary reviewer
+shengfa@google.com
+
+# secondary reviewer
 johnchen@chromium.org
 
 # COMPONENT: Test>WebDriver