docs: Update UI text of 'Alerting Policies'

Created by: patrickluoyu

Signed-off-by: Patrick-LuoYu patrickluo@yunify.com

What type of PR is this?

/kind documentation

What this PR does / why we need it:

Update UI text of 'Alerting Policies'.

Special notes for reviewers:

/assign @harrisonliu5

Please take a look. Thanks!

Does this PR introduce a user-facing change?

None