Explicitly specify units of gigabytes for RAM in Airflow DAG template

[kiersten-stokes]

Fixes an issue raised in this PR comment.

What changes were proposed in this pull request?

A "G" is added to the Airflow DAG template resources argument for the request_memory key.

Docs have also been updated to reflect that the units are in gigabytes for both KFP and Airflow.

How was this pull request tested?

Ran a pipeline with RAM resource amount specified.

$ kubectl describe pod <pod-name>
...
Ready:          False
    Restart Count:  0
    Requests:
      memory:  3G
    Environment:
      AWS_ACCESS_KEY_ID:           <set to the key 'AWS_ACCESS_KEY_ID' in secret 'airflow-cos-secret'>      Optional: false
      AWS_SECRET_ACCESS_KEY:       <set to the key 'AWS_SECRET_ACCESS_KEY' in secret 'airflow-cos-secret'>  Optional: false
      ELYRA_ENABLE_PIPELINE_INFO:  True
      ELYRA_RUNTIME_ENV:           airflow
      ELYRA_RUN_NAME:              test-ram-units-20221003T000000
...

Reviewed output of make docs

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[elyra-bot]

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[ptitzler]

LGTM!