Clarify docs on newline and auto-fill-mode

* doc/lispref/text.texi (Commands for Insertion):
* lisp/simple.el (newline): Do not mention conditions specific to
'do-auto-fill' under documentation of 'newline' (bug#36702).
1 job for master in 56 minutes and 53 seconds (queued for 3 seconds)
Status Job ID Name Coverage
failed #3664


Name Stage Failure
test-all Test
Makefile:319: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:294: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
make: *** [check-expensive] Error 2
Makefile:959: recipe for target 'check-expensive' failed
ERROR: Job failed: exit code 1