Improved grammar and made it clearer to the user

The use of the word 'temper' was a little misleading for users as it's not in the common lexicon. In the interests of keeping the UX as simple as possible, I propose that we change the default. :- )

packages/rocketchat-lib/server/startup/settings.js

@@ -585,7 +585,7 @@ RocketChat.settings.addGroup('Email', function() {
 			multiline: true,
 			i18nLabel: 'Footer'
 		});
-		return this.add('Email_Footer_Direct_Reply', '</td></tr></table></td></tr><tr><td border="0" cellspacing="0" cellpadding="0" width="100%" style="font-family: Helvetica,Arial,sans-serif; max-width: 800px; margin: 0 auto; padding: 1.5em; text-align: center; font-size: 8pt; color: #999;">You can directly reply to this email.<br>Do not temper reply email<br>Powered by <a href="https://rocket.chat" target="_blank">Rocket.Chat</a></td></tr></table></td></tr></table></html>', {
+		return this.add('Email_Footer_Direct_Reply', '</td></tr></table></td></tr><tr><td border="0" cellspacing="0" cellpadding="0" width="100%" style="font-family: Helvetica,Arial,sans-serif; max-width: 800px; margin: 0 auto; padding: 1.5em; text-align: center; font-size: 8pt; color: #999;">You can directly reply to this email.<br>Do not modify previous emails in the thread.<br>Powered by <a href="https://rocket.chat" target="_blank">Rocket.Chat</a></td></tr></table></td></tr></table></html>', {
 			type: 'code',
 			code: 'text/html',
 			multiline: true,