Update requests version used in contract tests (#199)

GitHub complains about relying on 2.31.0 so changing this to pull the
latest 2.x version, which is actually
https://github.com/open-telemetry/opentelemetry-python-contrib/tree/main/instrumentation
says it supports: `requests ~= 2.0`

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Author: thpierce

contract-tests/images/applications/requests/requirements.txt

@@ -1,4 +1,4 @@
 opentelemetry-distro==0.43b0
 opentelemetry-exporter-otlp-proto-grpc==1.22.0
 typing-extensions==4.9.0
-requests==2.31.0
+requests~=2.0