editors/slime: Update to fix build after editors/emacs-devel update

The 'when' argument of `make-obsolete' and related functions was recently
made mandatory. [1] Update to pull in an upstream fix to
`define-obsolete-variable-alias'. [2]

[1] https://github.com/emacs-mirror/emacs/commit/32c6732d16385f242b1109517f25e9aefd6caa5c
[2] https://github.com/slime/slime/commit/48bfe6cccfdf879cd7137b00eb2ca160665a92f8

Reported by: tcberner
Approved by: portmgr (blanket, build fix)