cleanup: remove old deprecation warnings

[kruskall]

remove old deprecation warnings

some are not relevant anymore completely wrong in 9

e.g

apm-server/internal/beatcmd/beat.go

Line 302 in 3132db6

logger.Warn("deprecation notice: support for macOS 10.15 will be removed in an upcoming version")

apm-server/internal/idxmgmt/supporter_factory.go

Line 52 in 3132db6

deprecatedConfigs := []deprecatedConfig{