docs(feature_flags): fix incorrect line markers and envelope name (aws-powertools#3792)

Co-authored-by: Ran Isenberg <ran.isenberg@ranthebuilder.cloud>

Author: ran-isenberg

docs/utilities/feature_flags.md

@@ -178,7 +178,7 @@ You can use `get_enabled_features` method for scenarios where you need a list of
 
 === "getting_all_enabled_features.py"
 
- ```python hl_lines="2 9 26"
+ ```python hl_lines="4 9 11 28"
  --8<-- "examples/feature_flags/src/getting_all_enabled_features.py"
  ```
 
@@ -472,7 +472,7 @@ For this to work, you need to use a JMESPath expression via the `envelope` param
 
 === "extracting_envelope.py"
 
- ```python hl_lines="7"
+ ```python hl_lines="10"
  --8<-- "examples/feature_flags/src/extracting_envelope.py"
  ```
 

examples/feature_flags/src/extracting_envelope.py

@@ -6,8 +6,8 @@
 app_config = AppConfigStore(
  environment="dev",
  application="product-catalogue",
- name="features",
- envelope="feature_flags",
+ name="feature_flags",
+ envelope="features",
 )
 
 feature_flags = FeatureFlags(store=app_config)