jammy-amd64-tf-a-build: Remove ArmClang 6.9

It's not referenced by any CI related repos (tf-a-ci-scripts or otherwise),
and clearly just a remnant from previous usage. As we prepare to switch
to UBL-enabled ArmClang version, remove any historical versions now.

Per https://linaro.atlassian.net/browse/TFC-515

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I1af232414dee625d7072acd945cbd985ed9e0d0f
1 file changed