chore: bump Earthfile ARG PE_VERSION to v4.8.8 (#537)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: spectro-prow

Earthfile

@@ -19,7 +19,7 @@ ARG SPECTRO_LUET_REPO=us-docker.pkg.dev/palette-images/edge
 ARG KAIROS_BASE_IMAGE_URL=$SPECTRO_PUB_REPO/edge
 
 # Spectro Cloud and Kairos tags.
-ARG PE_VERSION=v4.8.1
+ARG PE_VERSION=v4.8.8
 ARG KAIROS_VERSION=v3.5.9
 ARG K3S_FLAVOR_TAG=k3s1
 ARG RKE2_FLAVOR_TAG=rke2r1