[poincare] In Multiplication::shallowBeautify, when extracting the unit,

reduce without changing the unit in order to extract the right unit.

This fixes the following bug: simplify "πππ23*_cK"

poincare/include/poincare/expression_node.h

@@ -191,6 +191,17 @@ public:
       m_symbolicComputation(symbolicComputation),
       m_unitConversion(unitConversion)
     {}
+    static ReductionContext NonInvasiveReductionContext(ReductionContext reductionContext) {
+      return ReductionContext(
+          reductionContext.context(),
+          reductionContext.complexFormat(),
+          reductionContext.angleUnit(),
+          reductionContext.unitFormat(),
+          reductionContext.target(),
+          SymbolicComputation::DoNotReplaceAnySymbol,
+          UnitConversion::None
+        );
+    }
     Preferences::UnitFormat unitFormat() const { return m_unitFormat; }
     ReductionTarget target() const { return m_target; }
     SymbolicComputation symbolicComputation() const { return m_symbolicComputation; }

poincare/src/multiplication.cpp

@@ -423,7 +423,9 @@ Expression Multiplication::shallowBeautify(ExpressionNode::ReductionContext redu
   // Step 2: Handle the units
   if (hasUnit()) {
     Expression units;
-    self = deepReduce(reductionContext); // removeUnit has to be called on reduced expression
+    /* removeUnit has to be called on reduced expression but we want to modify
+     * the least the expression so we use the uninvasive reduction context. */
+    self = deepReduce(ExpressionNode::ReductionContext::NonInvasiveReductionContext(reductionContext));
     self = removeUnit(&units);
 
     if (self.isUndefined() || units.isUninitialized()) {