Happy BMO Push Day! (20211005.1)

the following changes have been pushed to bugzilla.mozilla.org:

(tag: https://github.com/mozilla-bteam/bmo/tree/release-20211004.1)

https://bugzil.la/1721830 : Remove Elasticsearch code from BMO as not used and will reduce code to maintain
https://bugzil.la/1729495 : Update showdependencygraph.cgi to not create a png file in data/webdot and instead include as base64 dataa
https://bugzil.la/1722612 : Add support for sending IP addresses of authentication failures and abusive behavior to the iprepd API for rate limiting
https://bugzil.la/1729270 : When changing severity from – to something, bugzilla complains that a comment is needed
https://bugzil.la/1674752 : Rate limit new account creation, password change, etc. emails