bug#59934: 28.2; Doc strings of `(kill|delete)-matching-lines'

[Drew Adams]

These two doc strings are _very_ similar.  The two commands are
presumably nearly the same, the difference being that one kills
to the `kill-ring' and the other just deletes.

Please consider, in each of these doc strings, adding a reference to the
other command.  E.g., "See also `<other>-matching-lines', which is
similar but <summarize the difference>."  That will make uses aware of
the existence of the other command.  Sometimes users don't consider, or
aren't even aware, of the difference between the two kinds of deletion.

You might also explicitly point out the use case for `kill-*', e.g.,
when giving the summary in the "See also": killing lets you subsequently
yank the matching lines somewhere.  Doesn't hurt to point this out
briefly.

In GNU Emacs 28.2 (build 2, x86_64-w64-mingw32)
 of 2022-09-13 built on AVALON
Windowing system distributor 'Microsoft Corp.', version 10.0.19044
System Description: Microsoft Windows 10 Pro (v10.0.2009.19044.2251)

Configured using:
 'configure --with-modules --without-dbus --with-native-compilation
 --without-compress-install CFLAGS=-O2'

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND THREADS TIFF TOOLKIT_SCROLL_BARS
XPM ZLIB

(NATIVE_COMP present but libgccjit not available)