Deprecation of fieldpass and fielddrop modifiers

[hackery]

influxdata/telegraf#12675 deprecated fieldpass and fielddrop. The changes have been in the github repo for over two years, but the change hasn't made it to docs.influxdata.com. Current releases are now logging deprecation warnings.

The configuration documentation seems to be generally out of date cf. github mainline.
https://github.com/influxdata/telegraf/blob/master/docs/CONFIGURATION.md

Relevant URLs

• https://docs.influxdata.com/telegraf/v1/configuration/