🐛 [parallelisation] Clean cancel function store after functions have been cancelled (#648)

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### Description

- fix a bug about the cancel function store which only grows even if not
needed



### Test Coverage

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Author: acabarbaye

changes/20250710210822.bugfix

@@ -0,0 +1 @@
+:bug: `[parallelisation]` Clean cancel function store after functions have been cancelled

utils/parallelisation/cancel_functions.go

@@ -23,11 +23,12 @@ func (s *CancelFunctionStore) RegisterCancelFunction(cancel ...context.CancelFun
 }
 
 func (s *CancelFunctionStore) Cancel() {
-	defer s.mu.RUnlock()
-	s.mu.RLock()
+	defer s.mu.Unlock()
+	s.mu.Lock()
 	for _, c := range s.cancelFunctions {
 		c()
 	}
+	s.cancelFunctions = []context.CancelFunc{}
 }
 
 func (s *CancelFunctionStore) Len() int {