fmt: fix inline comment formatting

[StunxFS]

 $ cat x.v
module main

/* Can't v fmt */
$ v fmt -w x.v
Reformatted file: x.v
$ cat x.v
module main

// Can't v fmt

Fix #25495.

[huly-for-github]

Connected to Huly®: V_0.6-26182

[spytheman]

Excellent work.
Thank you 🙇🏻.