Source upgrade doc: etcupdate no longer needs -B

Note: We confusingly have the instructions to build the system in the
build manual, the UPDATING file, and the Makefile. These will get out
of sync and will be harmful when they do.

Fixes:	ddf6fad029 ("etcupdate: Make nobuild the default")
Reviewed by:		jhb
Differential Revision:	https://reviews.freebsd.org/D57644

Makefile

@@ -85,7 +85,7 @@
 #  5.  `reboot'        (in single user mode: boot -s from the loader prompt).
 #  6.  `etcupdate -p'
 #  7.  `make installworld'
-#  8.  `etcupdate -B'
+#  8.  `etcupdate'
 #  9.  `make delete-old'
 # 10.  `reboot'
 # 11.  `make delete-old-libs' (in case no 3rd party program uses them anymore)

UPDATING

@@ -2571,7 +2571,7 @@ COMMON ITEMS:
 	<reboot in single user>				[3]
 	etcupdate -p					[5]
 	make installworld
-	etcupdate -B					[4]
+	etcupdate					[4]
 	make delete-old					[6]
 	<reboot>
 
@@ -2609,7 +2609,7 @@ COMMON ITEMS:
 	<reboot in single user>				[3]
 	etcupdate -p					[5]
 	make installworld
-	etcupdate -B					[4]
+	etcupdate					[4]
 	make delete-old					[6]
 	<reboot>
 

share/man/man7/build.7

@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd May 20, 2026
+.Dd June 18, 2026
 .Dt BUILD 7
 .Os
 .Sh NAME
@@ -1045,7 +1045,7 @@ After verifying that you do not need them, delete old files:
 cd /usr/src
 etcupdate -p
 make installworld
-etcupdate -B
+etcupdate
 make delete-old
 shutdown -r now
 .Ed