ref(chat): change initial input size to 1 line

css/_chat.scss

     font-size: 15px;
     line-height: 30px;
     padding: 5px;
-    max-height:150px;
-    min-height:35px;
     overflow-y: auto;
     resize: none;
     width: 100%;

react/features/chat/components/web/ChatInput.js

                         id = 'usermsg'
                         inputRef = { this._setTextAreaRef }
                         maxRows = { 5 }
-                        minRows = { 2 }
                         onChange = { this._onMessageChange }
                         onKeyDown = { this._onDetectSubmit }
                         placeholder = { this.props.t('chat.messagebox') }