Fix typo.

src/field_operation.inl

@@ -141,7 +141,7 @@ ARGS... args)
 
   // check that both fields holds the same type
   if(!field_have_same_type(field1, field2)) {
-    throw std::runtime_error("field1 and field2 dose not hold the same type");
+    throw std::runtime_error("field1 and field2 does not hold the same type");
   }
 
   if(std::holds_alternative<typeFloat>(field1)) {
@@ -255,7 +255,7 @@ field_operation3(
 
   if(!field_have_same_type(field1, field2) ||
      !field_have_same_type(field2, field3)) {
-    throw std::runtime_error("field1 and field2 dose not hold the same type");
+    throw std::runtime_error("field1 and field2 does not hold the same type");
   }
 
   if(std::holds_alternative<typeFloat>(field1)) {