fix wording and delete react jpeg file

src/components/utility/Navbar.jsx

@@ -47,7 +47,7 @@ const Navbar = (props) => {
         >
           <input
             className="form-control mr-sm-2"
-            placeholder="Search thread"
+            placeholder="Search a thread"
             aria-label="Search"
             required="false"
             {...bindSearch}