build(deps): bump fluent/fluent-bit from 3.1.2 to 3.1.5 in /sidecar/fluentbit #1343

Job	Run time
Build otelcol sidecar	4m 27s
Build tailing sidecar operator	1m 34s
Test Helm chart (fluentbit)	3m 45s
Test Helm chart (otelcol)	7m 30s
markdownlint	33s
Test Helm chart with custom configuration (fluentbit)	4m 52s
Test Helm chart with custom configuration (otelcol)	8m 22s
Test Helm chart with cert-manager (fluentbit)	4m 5s
Test resources created without Helm chart (fluentbit)	4m 8s
yamllint	8s
Test Helm chart with cert-manager (otelcol)	7m 50s
Test resources created without Helm chart (otelcol)	7m 46s
	55m 0s

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