[mimecast] Add ^8.0.0 stack compatibility

[andrewkroh]

Mimecast should be compatible with 8.0.0, but the kibana constraint only allows for 7.x.

integrations/packages/mimecast/manifest.yml

Line 12 in 5a2d68e

kibana.version: "^7.16.0"

[elasticmachine]

Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[andrewkroh]

This update can proceed, but should not be released to the EPR yet as per @jamiehynds.

Also the .owner.github value needs fixed to give it the proper team name.