bionic-amd64-tf-a-build: include Node.js v14 (LTS)

We are introducing additional Node.js tools that depend on Node.js, as
well as associated CI checks which use them (`commitlint`).

Change-Id: Ia4bbfe5aa57a0cc7acafa821d44270a4886a0853
Signed-off-by: Chris Kay <chris.kay@arm.com>
1 file changed