gitignore: Add tags file

Tags file is generated by ctags.

BUG=None
TEST=None

Change-Id: I61a3d0dff3d03152569c11dee01e53e89ab0f947
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/1990567
Tested-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Auto-Submit: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Commit-Queue: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Reviewed-by: Daniel Winkler <danielwinkler@google.com>
diff --git a/.gitignore b/.gitignore
index 6df12eb..fdc0f52 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,6 +11,7 @@
 *.pyc
 *.so
 *~
+tags
 
 # Anything created as a result of running a test
 results.*/