[chromedriver] Use explicit regular expression for sed

Sed behave the same on Mac and Linux for release script

Bug: chromedriver:3550
Change-Id: I5d24ef995297ec0a48d8ab289ce3eed815048cc7
Notry: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2315434
Commit-Queue: Shengfa Lin <shengfa@google.com>
Auto-Submit: Shengfa Lin <shengfa@google.com>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791312}

chrome/test/chromedriver/support/release/release.sh

@@ -61,8 +61,8 @@ gsutil cp $tgt/chromedriver_win32.zip gs://chromedriver/$version/chromedriver_wi
 
 echo -n $version > latest
 
-build=`echo $version | sed 's/\.[0-9]\+$//'`
-major=`echo $version | sed 's/\.[0-9.]\+$//'`
+build=`echo $version | sed -E 's/\.[0-9]+$//'`
+major=`echo $version | sed -E 's/\.[0-9.]+$//'`
 gsutil -h Content-Type:text/plain cp latest gs://chromedriver/LATEST_RELEASE_$build
 gsutil -h Content-Type:text/plain cp latest gs://chromedriver/LATEST_RELEASE_$major