config: fix default text/plain filter

; 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>

config/aerc.conf

@@ -222,7 +222,7 @@ reply-to-self=true
 # against (non-case-sensitive) and a comma, e.g. subject,text will match a
 # subject which contains "text". Use header,~regex to match against a regex.
 #subject,~^\[PATCH=colordiff
-text/plain=sed 's/^>\+.*/\x1b[2;36m&\x1b[0m/'
+text/plain=sed 's/^>\+.*/\x1b[36m&\x1b[0m/'
 #text/html=pandoc -f html -t plain
 #image/*=catimg -w $(tput cols) -