remove image builds from setup except those needed in the lab 2 walkthrough

[paulparkinson]

• also requires doc change to add ./build.sh step to the following labs...
  • lab2 before AI food pairing step
  • lab3 for all polyglot builds
  • observability lab for dblogexporter

[RichardExley]

This is now resolved or superseded by more recent thinking and constraints (pull limits)