Bump e2e test server constraints again

Author: shevisj

e2e-test-server/constraints.txt

@@ -17,7 +17,7 @@ libcst==0.3.18
 MarkupSafe==1.1.1
 mypy-extensions==0.4.3
 opentelemetry-api==1.4.0
-opentelemetry-sdk==1.1.0
+opentelemetry-sdk==1.4.0
 opentelemetry-semantic-conventions==0.20b0
 packaging==20.9
 proto-plus==1.18.1