Update index.md
What does this MR do?
Update runners cache s3 configuration
"With GitLab Runner 11.3.0, the configuration parameters related to S3 were moved to a dedicated [runners.cache.s3] section. The old format of the configuration with S3 configured directly in [runners.cache] section is still supported, but is deprecated with GitLab Runner 11.3.0. This support will be removed in GitLab Runner 12.0.0."
https://docs.gitlab.com/runner/configuration/advanced-configuration.html#the-runnerscache-section
This MR reflects this upcoming change of the runners s3 cache section.
Simplify configuration for Spot instances
You don't need to set a Spot instance bidding price:
"The request can include the maximum price that you are willing to pay per hour per instance (the default is the On-Demand price),"
https://docs.aws.amazon.com/en_en/AWSEC2/latest/UserGuide/how-spot-instances-work.html
Instances get terminated within two minutes notice
Correction on the Spot instance termination part: Instances get terminated within two minutes notice.
"When Amazon EC2 interrupts a Spot Instance, it provides a Spot Instance interruption notice, which gives the instance a two-minute warning before Amazon EC2 interrupts it"
https://docs.aws.amazon.com/en_en/AWSEC2/latest/UserGuide/how-spot-instances-work.html