TensorImpl::zeros() isnot pure virtual anymore

include/aidge/backend/TensorImpl.hpp

@@ -190,7 +190,9 @@ public:
     /**
      * @brief Set every element of the implementation to zero.
      */
-    virtual void zeros() = 0;
+    virtual void zeros() {
+        printf("Not implemented yet");
+    }
 
     constexpr const char *backend() const { return mBackend; }