rm duplicate validation task

Author: BSnelling

petab/v2/lint.py

@@ -979,14 +979,6 @@ def run(self, problem: Problem) -> ValidationIssue | None:
         return None
 
 
-class CheckExperimentalConditionsDefined(ValidationTask):
-    """A task to check that all conditions referenced by the experiments
-    are defined."""
-
-    def run(self, problem: Problem) -> ValidationIssue | None:
-        return None
-
-
 def get_valid_parameters_for_parameter_table(
     problem: Problem,
 ) -> set[str]:
@@ -1204,5 +1196,4 @@ def get_placeholders(
 #: Validation tasks that should be run PEtab SciML problems
 sciml_validation_tasks = default_validation_tasks + [
     CheckHybridizationTable(),
-    CheckExperimentalConditionsDefined(),
 ]