Update the fluent-bit documentation to 1.8.8

[rgl]

Is your feature request related to a problem? Please describe.

The documentation at https://grafana.com/docs/loki/latest/clients/fluentbit/ should be updated to latest fluent-bit.

Describe the solution you'd like

An updated documentation.

At least the output plugin name seems to have changed from grafana-loki to loki at https://docs.fluentbit.io/manual/pipeline/outputs/loki.

[owen-d]

related to #4648

[stale]

Hi! This issue has been automatically marked as stale because it has not had any
activity in the past 30 days.

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