dataproc: add encryption_config block to docs

[BBBmau]

Release Note Template for Downstream PRs (will be copied)

At first it seemed as though we didn't support encryption_config to be able to setup dataproc_workflow_templates with CMEK but the resource documentation simply lacked the top-level mention of encryption_config.

This will add the encryption_config block as well as an example for encryption_config block usage.

Link to the current dataproc_workflow_template documentation page

See Write release notes for guidance.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 1 file changed, 3 insertions(+), 2 deletions(-))

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 2 files changed, 96 insertions(+), 8 deletions(-))
google-beta provider: Diff ( 1 file changed, 93 insertions(+), 6 deletions(-))