Minor improvements to EDE and EIEIO manuals

For discussion, see the following threads:
https://lists.gnu.org/archive/html/emacs-devel/2020-05/msg00630.html
https://lists.gnu.org/archive/html/emacs-devel/2020-06/msg00099.html

* doc/misc/ede.texi (ede-generic-project): Clean up example.
* doc/misc/eieio.texi (Accessing Slots): Document slot-value as a
generalized variable and set-slot-value as obsolete.
(Predicates): Fix typo.
(Introspection): Document eieio-class-slots in place of the obsolete
object-slots.
1 job for emacs-27 in 90 minutes and 2 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #6250
test-all

01:30:02

 
Name Stage Failure
failed
test-all Test The script exceeded the maximum execution time set for the job
  ELC      lisp/faces-tests.elc
GEN lisp/faces-tests.log
ELC lisp/ffap-tests.elc
GEN lisp/ffap-tests.log
ELC lisp/filenotify-tests.elc
GEN lisp/filenotify-tests.log
ELC lisp/files-tests.elc
Pulling docker image gitlab/gitlab-runner-helper:x86_64-f100a208 ...
ERROR: Job failed: execution took longer than 1h30m0s seconds