Remove unnecessary contrib pkgs from docs install (#1470)

Author: NathanielRN

docs-requirements.txt

@@ -6,13 +6,7 @@ sphinx-autodoc-typehints~=1.10.2
 # doesn't work for pkg_resources.
 ./opentelemetry-api
 ./opentelemetry-sdk
--e "git+https://github.com/open-telemetry/opentelemetry-python-contrib.git#egg=opentelemetry-exporter-datadog&subdirectory=exporter/opentelemetry-exporter-datadog"
--e "git+https://github.com/open-telemetry/opentelemetry-python-contrib.git#egg=opentelemetry-instrumentation-grpc&subdirectory=instrumentation/opentelemetry-instrumentation-grpc"
 ./opentelemetry-instrumentation
--e "git+https://github.com/open-telemetry/opentelemetry-python-contrib.git#egg=opentelemetry-instrumentation-requests&subdirectory=instrumentation/opentelemetry-instrumentation-requests"
--e "git+https://github.com/open-telemetry/opentelemetry-python-contrib.git#egg=opentelemetry-instrumentation-wsgi&subdirectory=instrumentation/opentelemetry-instrumentation-wsgi"
--e "git+https://github.com/open-telemetry/opentelemetry-python-contrib.git#egg=opentelemetry-instrumentation-django&subdirectory=instrumentation/opentelemetry-instrumentation-django"
--e "git+https://github.com/open-telemetry/opentelemetry-python-contrib.git#egg=opentelemetry-instrumentation-flask&subdirectory=instrumentation/opentelemetry-instrumentation-flask"
 
 # Required by ext packages
 asgiref~=3.0