xfd: soft redirects should default to RFD

[NovemLinguae]

Requested by CX Zoom at https://en.wikipedia.org/wiki/Wikipedia_talk:Twinkle#Incorrect_XFD_target

XFDing a soft redirect is currently defaulting to various things such as MFD. Is supposed to default to RFD.

Appears to be a regression, since there are closed tickets on this issue:

• Failed to list a soft redirect at RFD #861
• Treat redirects with RfD template as redirects #1065

Test cases:

• https://en.wikipedia.org/wiki/Wikipedia:Gather
• https://en.wikipedia.org/wiki/Wikipedia:List_of_tags
• https://en.wikipedia.org/wiki/Wikipedia:Minerva