add changelog entry for stale ops-per-run increase #8

Job	Run time
opentelemetry-api	25s
opentelemetry-sdk	46s
opentelemetry-getting-started	20s
opentelemetry-semantic-conventions	20s
opentelemetry-propagator-jaeger	17s
opentelemetry-opentracing-shim	21s
opentelemetry-exporter-prometheus	22s
opentelemetry-opencensus-shim	23s
opentelemetry-test-utils	45s
opentelemetry-exporter-zipkin-proto-http	18s
opentelemetry-exporter-zipkin-json	18s
opentelemetry-exporter-otlp-proto-http	23s
opentelemetry-exporter-otlp-proto-common	21s
opentelemetry-exporter-opencensus	21s
opentelemetry-exporter-otlp-combined	29s
opentelemetry-exporter-zipkin-combined	18s
opentelemetry-propagator-b3	21s
opentelemetry-proto-gen-latest	18s
opentelemetry-exporter-otlp-proto-grpc-latest	19s
	7m 25s

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