build(deps): bump golang from 1.20.7 to 1.21.6 in /sidecar/fluentbit #1201

Job	Run time
Build tailing sidecar operator	1m 37s
Build otelcol sidecar	1m 19s
markdownlint	25s
Test Helm chart (fluentbit)	7m 38s
Test Helm chart (otelcol)	5m 39s
Test Helm chart with cert-manager (fluentbit)	8m 18s
Test resources created without Helm chart (fluentbit)	8m 10s
Test Helm chart with custom configuration (fluentbit)	8m 5s
Test resources created without Helm chart (otelcol)	6m 33s
Test Helm chart with custom configuration (otelcol)	5m 23s
Test Helm chart with cert-manager (otelcol)	5m 8s
yamllint	6s
	58m 21s

Provide feedback