pages/*: standardize mentioning subcommands without the main command (#13626)

* pages/*: standardize mentioning subcommands without the main command

* CONTRIBUTING: clarify that pages should only mention the subcommand

pages/linux/bpftool.md

@@ -1,7 +1,7 @@
 # bpftool
 
 > Inspect and manipulate eBPF programs and maps in a simple way.
-> Some subcommands such as `bpftool prog` have their own usage documentation.
+> Some subcommands such as `prog` have their own usage documentation.
 > More information: <https://manned.org/bpftool>.
 
 - List information about loaded `eBPF` programs:

pages/linux/btrfs.md

@@ -1,7 +1,7 @@
 # btrfs
 
 > A filesystem based on the copy-on-write (COW) principle for Linux.
-> Some subcommands such as `btrfs device` have their own usage documentation.
+> Some subcommands such as `device` have their own usage documentation.
 > More information: <https://btrfs.readthedocs.io/en/latest/btrfs.html>.
 
 - Create subvolume:

pages/linux/dpkg.md

@@ -1,7 +1,7 @@
 # dpkg
 
 > Debian package manager.
-> Some subcommands such as `dpkg deb` have their own usage documentation.
+> Some subcommands such as `deb` have their own usage documentation.
 > For equivalent commands in other package managers, see <https://wiki.archlinux.org/title/Pacman/Rosetta>.
 > More information: <https://manned.org/dpkg>.
 

pages/linux/ip.md

@@ -1,7 +1,7 @@
 # ip
 
 > Show/manipulate routing, devices, policy routing and tunnels.
-> Some subcommands such as `ip address` have their own usage documentation.
+> Some subcommands such as `address` have their own usage documentation.
 > More information: <https://www.manned.org/ip.8>.
 
 - List interfaces with detailed info:

pages/linux/toolbox.md

@@ -1,7 +1,7 @@
 # toolbox
 
 > Manage containerized command-line environments on Linux.
-> Some subcommands such as `toolbox create` have their own usage documentation.
+> Some subcommands such as `create` have their own usage documentation.
 > More information: <https://manned.org/toolbox.1>.
 
 - Run a `toolbox` subcommand: