fix(ci): correct typo in poetry memmap invocation

The variable `tf_build_path` does not exist; the correct name for the
build root is `tf_build_root`. Additionally, the memmap tool invocation
should be non-fatal, allowing errors to be ignored.

Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
Change-Id: Ibc68ae63ec2276b1f591096cffe6eeec388e525d
1 file changed