scripts: Eliminate CI variable as it is not longer used

This PR removes the CI variable which is not longer being used or valid
in the kata containers repository. The CI variable was used when we
were using jenkins and scripts setups which are not longer supported.

Signed-off-by: Gabriela Cervantes <gabriela.cervantes.tellez@intel.com>

tools/osbuilder/rootfs-builder/rootfs.sh

@@ -495,7 +495,6 @@ build_rootfs_distro()
 			--env AGENT_BIN="${AGENT_BIN}" \
 			--env AGENT_INIT="${AGENT_INIT}" \
 			--env ARCH="${ARCH}" \
-			--env CI="${CI}" \
 			--env MEASURED_ROOTFS="${MEASURED_ROOTFS}" \
 			--env KERNEL_MODULES_DIR="${KERNEL_MODULES_DIR}" \
 			--env LIBC="${LIBC}" \