define-obsolete-function-alias needs a third argument

[seelabs]

Describe the bug

In emacs 28, the when argument of the function define-obsolete-function-alias is no longer optional. When loading rtags, it fails with wrong-number-of-arguments (3 . 4), 2

To Reproduce
Steps to reproduce the behavior:

1. Use a development version of emacs (emacs 28)
2. Load the rtags library with "m-x load-library rtags"
3. See the error

Environment (please complete the following information):

• OS/Version: popos 20.04
• RTags(rdm,rc): 2.41 3933938
• Emacs: 28.0.50
• LLVM/Clang: 11

Additional context

If I modify the file rtags.el and change line 4694 so it reads:
(define-obsolete-function-alias 'rtags-start-process-maybe 'rtags-start-process-unless-running "xxx")
then things work correctly. I don't know what the correct value for "xxx" should be, but any string seems to get past the error.

[zflat]

The 'when' argument of make-obsolete and related functions is
mandatory since https://emba.gnu.org/emacs/emacs/-/commit/32c6732d16385f242b1109517f25e9aefd6caa5c

[Andersbakken]

Should be fixed now. Thanks.