docs: Align keyword-only upgrade section with client v3 guide wording

Author: vdusek

docs/04_upgrading/upgrading_to_v4.md

@@ -10,33 +10,23 @@ This guide lists the breaking changes between Apify Python SDK v3.x and v4.0.
 
 Support for Python 3.10 has been dropped. The Apify Python SDK v4.x now requires Python 3.11 or later — make sure your environment is on a compatible version before upgrading.
 
-## Keyword-only arguments for secondary parameters
+## Keyword-only arguments
 
-Several `Actor` methods had a `*` separator inserted into their signatures, so optional/secondary parameters can no longer be passed positionally. The "subject" arguments (e.g. `key` on `get_value`, `data` on `push_data`, `event_name` on `charge`) remain positional; only the parameters that follow them are affected.
-
-### Affected APIs
-
-- `Actor.get_value(key, *, default_value=None)`
-- `Actor.push_data(data, *, charged_event_name=None)`
-- `Actor.charge(event_name, *, count=1)`
-- `Actor.use_state(default_value=None, *, key=None, kvs_name=None)`
-
-The same treatment was applied to the `ChargingManager.charge(event_name, *, count=1)` method returned by `Actor.get_charging_manager()`.
-
-### Migration
-
-Before (v3):
+Secondary parameters on these methods can no longer be passed positionally.
 
 ```python
+# Before
 value = await Actor.get_value('my-key', default_value)
 await Actor.push_data(data, 'my-event')
 await Actor.charge('my-event', 5)
-```
-
-After (v4):
 
-```python
+# After
 value = await Actor.get_value('my-key', default_value=default_value)
 await Actor.push_data(data, charged_event_name='my-event')
 await Actor.charge('my-event', count=5)
 ```
+
+Affected signatures:
+
+- `Actor` — `get_value`, `push_data`, `charge`, `use_state`.
+- `ChargingManager` — `charge`.