CREDITS, MAINTAINERS, docs/process/howto: Update man-pages' maintainer

Michael retired from maintaining the Linux man-pages project in 2021.
See commit 06e72cb19c74d3b1d661609c698ee26d7b6e4d7e ("CONTRIBUTING,
README, lsm: Remove mtk as maintainer") in the Linux man-pages
repository.

Add him to CREDITS.

Reported-by: Ahelenia Ziemiańska <[e-mail]>
Link: <https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?id=06e72cb19c74d3b1d661609c698ee26d7b6e4d7e>
Acked-by: Randy Dunlap <[e-mail]>
Cc: Michael Kerrisk <[e-mail]>
Cc: Michael Kerrisk <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Signed-off-by: Alejandro Colomar <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

CREDITS

···
 S: 160 00 Praha 6
 S: Czech Republic
 
+N: Michael Kerrisk
+E: [e-mail]
+W: https://man7.org/
+P: 4096R/3A35CE5E E522 595B 52ED A4E6 BFCC  CB5E 8561 9911 3A35 CE5E
+D: Maintainer of the Linux man-pages project
+D: Linux man pages online, at <https://man7.org/linux/man-pages/>
+
 N: Niels Kristian Bech Jensen
 E: [e-mail]
 D: Miscellaneous kernel updates and fixes.

Documentation/process/howto.rst

···
 When a kernel change causes the interface that the kernel exposes to
 userspace to change, it is recommended that you send the information or
 a patch to the manual pages explaining the change to the manual pages
-maintainer at [e-mail], and CC the list
[e-mail].
+maintainer at [e-mail], and CC the list [e-mail].
 
 Here is a list of files that are in the kernel source tree that are
 required reading:

MAINTAINERS

···
 F:	include/linux/mailbox/arm_mhuv2_message.h
 
 MAN-PAGES: MANUAL PAGES FOR LINUX -- Sections 2, 3, 4, 5, and 7
-M:	Michael Kerrisk <[e-mail]>
+M:	Alejandro Colomar <[e-mail]>
 L:	[e-mail]
 S:	Maintained
 W:	http://www.kernel.org/doc/man-pages