Chats: isSearch --> theme='search'

app/soapbox/features/chats/components/chat-search-input.tsx

@@ -29,7 +29,7 @@ const ChatSearchInput: React.FC<IChatSearchInput> = ({ value, onChange, onClear
       className='rounded-full'
       value={value}
       onChange={onChange}
-      isSearch
+      theme='search'
       append={
         <button onClick={onClear}>
           <Icon

app/soapbox/features/chats/components/chat-search/chat-search.tsx

@@ -110,7 +110,7 @@ const ChatSearch = () => {
               className='rounded-full'
               value={value || ''}
               onChange={(event) => setValue(event.target.value)}
-              isSearch
+              theme='search'
               append={
                 <button onClick={clearValue}>
                   <Icon