Changes `randomization` to `events` in Digit envs (#3033)

# Description

Change `randomization` to `events` in Digit envs

## Type of change

- Bug fix (non-breaking change which fixes an issue)

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

source/isaaclab_tasks/isaaclab_tasks/manager_based/loco_manipulation/tracking/config/digit/loco_manip_env_cfg.py

@@ -246,5 +246,5 @@ class DigitLocoManipEnvCfg_PLAY(DigitLocoManipEnvCfg):
         # Disable randomization for play.
         self.observations.policy.enable_corruption = False
         # Remove random pushing.
-        self.randomization.base_external_force_torque = None
-        self.randomization.push_robot = None
+        self.events.base_external_force_torque = None
+        self.events.push_robot = None

source/isaaclab_tasks/isaaclab_tasks/manager_based/locomotion/velocity/config/digit/flat_env_cfg.py

@@ -33,5 +33,5 @@ class DigitFlatEnvCfg_PLAY(DigitFlatEnvCfg):
         # Disable randomization for play.
         self.observations.policy.enable_corruption = False
         # Remove random pushing.
-        self.randomization.base_external_force_torque = None
-        self.randomization.push_robot = None
+        self.events.base_external_force_torque = None
+        self.events.push_robot = None

source/isaaclab_tasks/isaaclab_tasks/manager_based/locomotion/velocity/config/digit/rough_env_cfg.py

@@ -262,5 +262,5 @@ class DigitRoughEnvCfg_PLAY(DigitRoughEnvCfg):
         # Disable randomization for play.
         self.observations.policy.enable_corruption = False
         # Remove random pushing.
-        self.randomization.base_external_force_torque = None
-        self.randomization.push_robot = None
+        self.events.base_external_force_torque = None
+        self.events.push_robot = None