chore: Update text for 'BetaFeaturesNotEnabled' exception. (#4581)

## Context
The exception message was not clear. The message was slightly
inaccurate, as it suggested that beta features can only be enabled via a
Python call.

## Change Summary
The exception message was updated to be more precise about the need of
the python call.

## Impact
Users will see the updated error message when 'BetaFeaturesNotEnabled'
is raised.

---------

Co-authored-by: pyansys-ci-bot <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: 3 people

doc/changelog.d/4581.maintenance.md

@@ -0,0 +1 @@
+Update text for 'BetaFeaturesNotEnabled' exception.

src/ansys/fluent/core/exceptions.py

@@ -56,9 +56,13 @@ class BetaFeaturesNotEnabled(RuntimeError):
     """Raised when a beta feature is accessed without enabling beta features."""
 
     def __init__(self, feature_name: str | None = None) -> None:
+        base_message = (
+            " is a Fluent beta feature. To enable it from Python "
+            "call '<session>.enable_beta_features()'."
+        )
         message = (
-            f"The feature '{feature_name}' is not available until 'enable_beta_features()' has been called."
+            f"'{feature_name}'" + base_message
             if feature_name
-            else "This feature is not available until 'enable_beta_features()' has been called."
+            else "This " + base_message
         )
         super().__init__(message)