Doc: remove notes about the version vacuumdb options are valid from

Doc: remove notes about the version vacuumdb options are valid from

Here we remove the notes which mention which version the given vacuumdb
option is available from.  There are now 11 of these notes and they're
both quite untidy and take up far more space than they seem to be worth.
On running a print preview of the compiled HTML, removing these notes
saves about 1 A4 page (~20% less space).

If people need to see which options are available on older versions, then
consulting the documents for that version seems like a good idea.  In any
case, when using newer vacuumdb versions on older servers, the user will
receive an error if they try to use an unsupported option.

Additionally, 3 of the notes are warning about the option only being
available from PostgreSQL 9.6 and later.  That version's support ended 2.5
years ago.  So, it's quite clear that the value of these notes diminishes
over time.

Discussion: https://postgr.es/m/CAApHDvrCQn6tupx2R67VL9RP1Qy4dDuWKRvt4jaB0vk2akQchw@mail.gmail.com