[form recognizer] remove duplicate platform info in user agent (#12124)

Author: iscai-msft

sdk/formrecognizer/azure-ai-formrecognizer/azure/ai/formrecognizer/_user_agent.py

@@ -4,9 +4,6 @@
 # Licensed under the MIT License.
 # ------------------------------------
 
-import platform
 from ._version import VERSION
 
-USER_AGENT = "ai-formrecognizer/{} Python/{} ({})".format(
-    VERSION, platform.python_version(), platform.platform()
-)
+USER_AGENT = "ai-formrecognizer/{}".format(VERSION)