add assertTraceResponseHeaderMatchesSpan method (#2159)
add assertTraceResponseHeaderMatchesSpan method (#2159)

* add assertTraceResponseHeaderMatchesSpan method

* fix lint

Co-authored-by: Diego Hurtado <2bc8d855c0e6dd74eb47b0b9f8b97160279b08b1@users.noreply.github.com>
open-telemetry/opentelemetry-python,open-telemetry/opentelemetry-python