Update Debian package installation documentation (#22405)
Update Debian package installation documentation (#22405)

#9261 added a warning about the use of `add-apt-repository` which is becoming obsolete over time as new distribution releases include later versions of `add-apt-repository` which don't automatically add the `deb-src` line. This change updates the documentation to make the block a note rather than a warning and adds two other reasons for avoiding `add-apt-repository` which are still relevant: avoiding edits to a system shared file and not requiring a large number of non-default packages to add one line of text to a file.
strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc