docs: remove fga_client.close() from README (#191)

Author: JsMelix

README.md

@@ -142,7 +142,6 @@ async def main():
     # Enter a context with an instance of the OpenFgaClient
     async with OpenFgaClient(configuration) as fga_client:
         api_response = await fga_client.read_authorization_models()
-        await fga_client.close()
         return api_response
 ```
 
@@ -168,7 +167,6 @@ async def main():
     # Enter a context with an instance of the OpenFgaClient
     async with OpenFgaClient(configuration) as fga_client:
         api_response = await fga_client.read_authorization_models()
-        await fga_client.close()
         return api_response
 ```
 
@@ -197,7 +195,6 @@ async def main():
     # Enter a context with an instance of the OpenFgaClient
     async with OpenFgaClient(configuration) as fga_client:
         api_response = await fga_client.read_authorization_models()
-        await fga_client.close()
         return api_response
 ```