use dynamic service accounts in generated IAM doc examples

[nsamartsev]

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compute: use dynamic service accounts in generated IAM doc examples

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes for commit be4a97b:

Diff report

Your PR generated the following diffs in downstream repositories:

Repository	Diff Link	Changes
google provider	View Diff	125 files changed, 2973 insertions(+), 489 deletions(-)
google-beta provider	View Diff	125 files changed, 2973 insertions(+), 489 deletions(-)