Update IAM policy binding permissions in README

[duemir]

To prepare the list for the "Minimum Cpu Platform" plugin needs to get the Zone. availableCpuPlatforms field of the zone is the source.

https://docs.cloud.google.com/compute/docs/reference/rest/v1/zones/get is the API doc which states that compute.zones.get is required.

Testing done

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed

[gbhat618]

had you run into any errors ? (not that I see any problem with it, just curious how to came across investigating it 😄 )

[duemir]

@gbhat618 I just kept getting "Error retrieving cpu Platforms". It is returned as a combobox/dropdown (don't remember which it is exactly) item so it is then saved as "minCpuPlatform". Since it is an error message, not a CPU Platform, the instance configuration is impossible to use.

google-compute-engine-plugin/src/main/java/com/google/jenkins/plugins/computeengine/InstanceConfiguration.java

Lines 1001 to 1005 in 56d37cb

	} catch (IOException ioe) {
	items.clear();
	items.add("Error retrieving cpu Platforms");
	return items;
	} catch (IllegalArgumentException iae) {

It does not log the exception, so I had no idea of the cause. I read a bit of library source code which led me to https://docs.cloud.google.com/compute/docs/reference/rest/v1/zones/get which said it required compute.zones.get. So I added the permission to the role, which fixed the issue for me.