Fix documentation of inhibit-modification-hooks in overlays + text properties

Fix documentation of inhibit-modification-hooks in overlays + text properties

This fixes bug #25111.

* doc/lispref/display.text (Overlay Properties): For the hook property
modification-hooks, state that inhibit-modification-hooks is bound to non-nil
when calling its functions.  This also applies to insert-in-front-hooks and
insert-behind-hooks, which refer to modification-hooks.

* doc/lispref/text.texi (Special Properties): For the hook property
modification-hooks, state that inhibit-modification-hooks is NOT bound to
non-nil when calling its functions.  For the hooks insert-in-fron-hooks and
insert-behind-hooks, state that that variable does get bound to non-nil.