; is a special character for the INI format. It starts a comment and
apparently cannot be escaped nor quoted. This causes the default
text/plain filter to be truncated and causes this obscure error when
viewing a message:
sh: 1: Syntax error: Unterminated quoted string
Debugging shows that the filter command is:
sh -c "sed 's/^>\\+.*/\\x1b[2"
Remove the explicit dim style. It should be the default anyway.
Fixes: 7c3ce816c8 ("config: set a default filter for text/plain")
Signed-off-by: Robin Jarry <robin@jarry.cc>