Revert "[BugFix] Changing the dm_control import to fail if not installed (#515)"

This reverts commit d194735.

Author: Silvestre Bahi

torchrl/envs/libs/dm_control.py

@@ -272,11 +272,6 @@ class DMControlEnv(DMControlWrapper):
     """
 
     def __init__(self, env_name, task_name, **kwargs):
-        if not _has_dmc:
-            raise ImportError(
-                "dm_control python package was not found."
-                "Please install this dependency."
-            )
         kwargs["env_name"] = env_name
         kwargs["task_name"] = task_name
         super().__init__(**kwargs)