refactor mails

uffd/selfservice/templates/mailverification.mail.txt

 Hi {{ user.displayname }},
 
-you have requested to change your mail address.
-To confirm the change, please visit this URL: {{ url_for('selfservice.token_mail', token=token, _external=True) }} 
-**Please note this link is only valid for 48h**
+you have requested to change your mail address. To confirm the change, please visit the following url:
+{{ url_for('selfservice.token_mail', token=token, _external=True) }}
 
-Kind regards,
-uffd
+**The link is valid for 48h**

uffd/selfservice/templates/newuser.mail.txt

 Hi {{ user.displayname }},
 
-welcome to the CCCV infrastructure.
-An account was created for you, visit this url to set your password: {{ url_for('selfservice.token_password', token=token, _external=True) }}
-**Please note this link is only valid for 48h**
+welcome to the CCCV infrastructure.  An account was created for you, please visit the following url to set your
+password: {{ url_for('selfservice.token_password', token=token, _external=True) }}
 
-You can find more information here: https://docs.cccv.de/
+**The link is valid for 48h**
 
-If you have no idea why someone would create an account for you to be used for the next CCC event organization, please contact it@cccv.de.
+You can find more information at https://docs.cccv.de/.
 
-Kind regards,
-uffd
+If you have no idea why someone would create an account for you to be used for the next CCC event organization, please
+contact the infra team at it@cccv.de.
\ No newline at end of file

uffd/selfservice/templates/passwordreset.mail.txt

 Hi {{ user.displayname }},
 
-you have requested a password reset.
-To reset your password, visit this url: {{ url_for('selfservice.token_password', token=token, _external=True) }} 
-**Please note this link is only valid for 48h**
+you have requested a password reset. To reset your password, visit the following url:
+{{ url_for('selfservice.token_password', token=token, _external=True) }}
 
-If you did not request a password reset, you do not need to do anything.
+**The link is valid for 48h**
 
-Kind regards,
-uffd
+If you did not request a password reset, please ignore this message.