doc: make instructions to get an updated cephadm common

As discussed in person and over the ceph orch weekly, we want all users
to use a recent supported version of cephadm. Previously, the
instructions only had those downloading cephadm with curl using the
"add-repo" and "install" commands to get a up-to-date cephadm build.
According to ADK we've seen cases of users get "old" distro packages
in the past. Change the instructions so that the "update cephadm" steps
are common after acquiring a "bootstrap copy" of cephadm.

Note: This commit is a cherry-pick of
d7921e8, which was introduced by John
Mulligan in ceph#48180. This is one of
three commits introduced in that PR, and this cherry-pick cleans up
omissions I (Zac Dover) inadvertently introduced while attempting to
rectify the merge conflicts in ceph#51843.
I expect that two more cherry-picked commits will follow this one.

Signed-off-by: John Mulligan <[email protected]>
(cherry picked from commit d7921e8)

Author: phlogistonjohn

doc/cephadm/install.rst

@@ -171,46 +171,6 @@ A successful ``which cephadm`` command will return this:
 
    /usr/sbin/cephadm
 
-* Although the standalone cephadm is sufficient to get a cluster started, it is
-  convenient to have the ``cephadm`` command installed on the host.  To install
-  the packages that provide the ``cephadm`` command, run the following
-  commands:
-
-update cephadm
---------------
-
-The cephadm binary can be used to bootstrap a cluster and for a variety
-of other management and debugging tasks. The Ceph team strongly recommends
-using an actively supported version of cephadm. Additionally, although
-the standalone cephadm is sufficient to get a cluster started, it is
-convenient to have the ``cephadm`` command installed on the host. Older or LTS
-distros may also have ``cephadm`` packages that are out-of-date and
-running the commands below can help install a more recent version
-from the Ceph project's repositories.
-
-To install the packages provided by the Ceph project that provide the
-``cephadm`` command, run the following commands:
-
-.. prompt:: bash #
-   :substitutions:
-
-   ./cephadm add-repo --release |stable-release|
-   ./cephadm install
-
-Confirm that ``cephadm`` is now in your PATH by running ``which`` or
-``command -v``:
-
-.. prompt:: bash #
-
-   which cephadm
-
-A successful ``which cephadm`` command will return this:
-
-.. code-block:: bash
-
-   /usr/sbin/cephadm
-
-
 
 Bootstrap a new cluster
 =======================