feat(DeepLinkingMobilePage): fix nested iframe button

react/features/deep-linking/components/DeepLinkingMobilePage.web.js

                     </p>
                     <a
                         href = { this._generateDownloadURL() }
-                        onClick = { this._onDownloadApp } >
+                        onClick = { this._onDownloadApp } 
+                        target = "_blank">
                         <button className = { downloadButtonClassName }>
                             { t(`${_TNS}.downloadApp`) }
                         </button>
                     <a
                         className = { `${_SNS}__href` }
                         href = { this.state.joinURL }
-                        onClick = { this._onOpenApp }>
+                        onClick = { this._onOpenApp }
+                        target = "_blank">
                         {/* <button className = { `${_SNS}__button` }> */}
                         { t(`${_TNS}.openApp`) }
                         {/* </button> */}