rm underscore in feature_flags to keep consistent w python sdk

Author: aliu39

docs/platforms/python/integrations/feature_flags/index.mdx renamed to docs/platforms/python/integrations/featureflags/index.mdx

@@ -22,7 +22,7 @@ Add `FeatureFlagsIntegration()` to your `integrations` list:
 
 ```python
 import sentry_sdk
-from sentry_sdk.integrations.feature_flags import FeatureFlagsIntegration
+from sentry_sdk.integrations.featureflags import FeatureFlagsIntegration
 
 sentry_sdk.init(
     dsn="___PUBLIC_DSN___",
@@ -38,7 +38,7 @@ The integration is tested by calling the `add_feature_flag` API before capturing
 
 ```python
 import sentry_sdk
-from sentry_sdk.integrations.feature_flags import add_feature_flag
+from sentry_sdk.integrations.featureflags import add_feature_flag
 
 add_feature_flag('hello', False)