Fixes https://github.com/gitpod-io/gitpod/issues/8740
`definitely-gp` is being deprecated soon, and hence
it is important to be disabled by default. Once it
is fully deprecated, even this option has to be removed.
For now, The following changes have been made:
- Update the `definitelyGpDisabled` option to be true, Thus
disabling it by default both in the `installer` and `chart`.
- Update the airgap docs to remove a mention of this.
Signed-off-by: Tarun Pothulapati <tarun@gitpod.io>
