Remove any duplicate quotes in the email sender

If the "From" header of the email feedback contains quotes, these will be escaped, and the result is quoted again.
It seems like the backslash is then stripped by some mail servers, which results in a From header like this:
> From: "John Doe via "My Organization (Support Team)"" <support@my.org>

The result seems to confuse email clients. We received a mail from a user whose mail client compiled strange email replies out of this, e.g. support"@my.org.

There are two possible ways to solve this:

a) Remove the quotes at the beginning & end of the name:
> From: John Doe via "My Organization (Support Team)" <support@my.org>

b) Remove the quotes within the name, but leave leading and trailing quotes:
> From: "John Doe via My Organization (Support Team)" <support@my.org>

This change will implement the 2nd variant, which should work well with any mail clients...