hier(7): remove text describing /usr/src layout

It poses a maintenance burden, since much of the information is
duplicated in the src tree's README.md file. Readers who are interested
enough in learning about the structure of the src tree can download it,
or browse the README online. Have hier(7) just point them there instead.

PR:		261349
Discussed with:	freebsd-arch@, freebsd-doc@ lists
Reviewed by:	imp, emaste
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D37135

Author: mhorne

README.md

@@ -33,6 +33,7 @@ Source Roadmap:
 | share | Shared resources. |
 | stand | Boot loader sources. |
 | sys | Kernel sources (see [sys/README.md](sys/README.md)). |
+| targets | Support for experimental `DIRDEPS_BUILD` |
 | tests | Regression tests which can be run by Kyua.  See [tests/README](tests/README) for additional information. |
 | tools | Utilities for regression testing and miscellaneous tasks. |
 | usr.bin | User commands. |

share/man/man7/hier.7

@@ -28,7 +28,7 @@
 .\"	@(#)hier.7	8.1 (Berkeley) 6/5/93
 .\" $FreeBSD$
 .\"
-.Dd August 4, 2022
+.Dd November 1, 2022
 .Dt HIER 7
 .Os
 .Sh NAME
@@ -641,127 +641,10 @@ see
 .It Pa src/
 .Fx
 source code; see
-.Xr development 7
-.Pp
-.Bl -tag -width "kerberos5/" -compact
-.It Pa bin/
-source code for files in /bin
-.It Pa cddl/
-utilities covered by the Common Development and Distribution License
-.It Pa contrib/
-source code for contributed software
-.It Pa crypto/
-source code for contributed cryptography software
-.It Pa etc/
-source code for files in
-.Pa /etc
-.It Pa gnu/
-utilities covered by the GNU General Public License
-.It Pa include/
-source code for files in
-.Pa /usr/include
-.It Pa kerberos5/
-build infrastructure for Kerberos version 5
-.It Pa lib/
-source code for files in
-.Pa /lib
-and
-.Pa /usr/lib
-.It Pa libexec/
-source code for files in
-.Pa /usr/libexec
-.It Pa release/
-files required to produce a
-.Fx
-release
-.It Pa rescue/
-source code for files in
-.Pa /rescue
-.It Pa sbin/
-source code for files in
-.Pa /sbin
-.It Pa secure/
-build directory for files in
-.Pa /usr/src/crypto
-.It Pa share/
-source for files in
-.Pa /usr/share
-.It Pa stand/
-boot loader source code
-.It Pa sys/
-kernel source code
-.Bl -tag -width Fl -compact
-.It Pa amd64/
-AMD64 architecture support
-.It Pa arm/
-ARM architecture support
-.It Pa arm64/
-ARMv8 architecture support
-.It Pa cam/
-.Xr cam 4
-and
-.Xr ctl 4
-.It Pa cddl/
-CDDL-licensed optional sources, including ZFS
-and DTrace
-.It Pa ddb/
-.Xr ddb 4
-.It Pa fs/
-most filesystems
-.It Pa dev/
-device drivers
-.It Pa geom/
-.Xr geom 4
-.It Pa i386/
-i386 (32 bit) architecture support
-.It Pa kern/
-main part of the kernel
-.It Pa net80211/
-.Xr net80211 4
-.It Pa netgraph/
-.Xr netgraph 4
-.It Pa netinet/
-.Xr inet 4
-.It Pa netinet6/
-.Xr inet6 4
-.It Pa netipsec/
-.Xr ipsec 4
-.It Pa netpfil/
-.Xr ipfw 4
-and
-.Xr pf 4
-.It Pa opencrypto/
-.Xr crypto 7
-.It Pa powerpc/
-PowerPC/POWER architecture support
-.It Pa riscv/
-RISC-V architecture support
-.It Pa security/
-.Xr audit 4
-and
-.Xr mac 4
-.It Pa sys/
-kernel headers
-.It Pa ufs/
-Unix File System
-.It Pa x86/
-code shared by AMD64 and i386 architectures
-.El
-.It Pa targets/
-support for experimental DIRDEPS_BUILD
-.It Pa tests/
-source code for files in
-.Pa /usr/tests
-.It Pa tools/
-tools used for maintenance and testing of
-.Fx
-.It Pa usr.bin/
-source code for files in
-.Pa /usr/bin
-.It Pa usr.sbin/
-source code for files in
-.Pa /usr/sbin
-.El
+.Xr development 7 .
+The layout of the source tree is described by the top-level
+.Pa README.md
+file.
 .Pp
 .It Pa tests/
 The