docs: Fix SUPPORT matrix generation after a5968a553f6a

docs: Fix SUPPORT matrix generation after a5968a553f6a

Commit a5968a553f6a "SUPPORT.MD: Correct the amount of physical memory
supported for Arm" added a support statement split over two lines.

Unfortunately, docs/support-matrix-generate throw an error for it:

    Generating support matrix (origin/stable-NN )
    + docs/support-matrix-generate HEAD https://xenbits.xen.org/docs/unstable/SUPPORT.html origin/stable-NN https://xenbits.xen.org/docs/NN-testing/SUPPORT.html
    Status, x86: Supported up to 8 TiB. Hosts with more memory are
                 supported, but not security supported.
    Status, Arm32: Supported up to 12 GiB
    Status, Arm64: Supported up to 2 TiB
    ^ cannot parse status codeblock line:
                 supported, but not security supported.
     ? at docs/parse-support-md line 172, <F> chunk 1.

It would be good to allow split support statement (to keep lines below
80 characters) but my knowledge of the script is very limited.

Therefore, workaround the error by describing the support statement
in one long line.

Fixes: a5968a553f6a "SUPPORT.MD: Correct the amount of physical memory supported for Arm"
Signed-off-by: Julien Grall <jgrall@amazon.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>