fix styling of default message

libs/remix-ui/solidity-uml-gen/src/lib/solidity-uml-gen.tsx

@@ -78,13 +78,13 @@ export function RemixUiSolidityUmlGen ({ updatedSvg, loading }: RemixUiSolidityU
 
   const DefaultInfo = () => (
     <div className="d-flex flex-column justify-content-center align-items-center mt-5 ml-5">
-      <h2 className="h2 align-self-start"><p>To view your contract as a UML Diagram</p></h2>
+      <h3 className="h3 align-self-start text-dark"><p>To view your contract as a UML Diagram</p></h3>
       <ul className="ml-3 justify-content-start align-self-start">
         <li>
-          <h3 className="h4 align-self-start"><p>Right click on your contract file</p></h3>
+          <h5 className="h5 align-self-start text-dark"><p>Right click on your contract file</p></h5>
         </li>
         <li>
-          <h3 className="h4 align-self-start"><p>Click on <b>Generate UML</b></p></h3>
+          <h5 className="h5 align-self-start text-dark"><p>Click on <b>Generate UML</b></p></h5>
         </li>
       </ul>
     </div>