fixed typo

src/storm/logic/ShieldExpression.cpp

@@ -22,7 +22,7 @@ namespace storm {
             return type == storm::logic::ShieldingType::PostSafety;
         }
 
-        bool ShieldExpression::isOptiomalShield() const {
+        bool ShieldExpression::isOptimalShield() const {
             return type == storm::logic::ShieldingType::Optimal;
         }
 

src/storm/logic/ShieldExpression.h

@@ -22,7 +22,7 @@ namespace storm {
             bool isRelative() const;
             bool isPreSafetyShield() const;
             bool isPostSafetyShield() const;
-            bool isOptiomalShield() const;
+            bool isOptimalShield() const;
 
             double getValue() const;