Fixed clang-tidy warnings

src/common/model/enums.cc

@@ -140,14 +140,14 @@ diagram_t from_string(const std::string &s)
 {
     if (s == "class")
         return diagram_t::kClass;
-    else if (s == "sequence")
+    if (s == "sequence")
         return diagram_t::kSequence;
-    else if (s == "include")
+    if (s == "include")
         return diagram_t::kInclude;
-    else if (s == "package")
+    if (s == "package")
         return diagram_t::kPackage;
-    else
-        throw std::runtime_error{"Invalid diagram type: " + s};
+
+    throw std::runtime_error{"Invalid diagram type: " + s};
 }
 
 } // namespace clanguml::common::model