Update disable-extended-support.md - missing quotation marks in command

[noobtron]

Issue #, if available:
they greyed out command in Disable EKS extended support (AWS CLI) is not recognized without quotation marks around supportType = STANDARD

Description of changes:
add quotation marks around "supportType = STANDARD"

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[aaroniscode]

Another option is to just remove the spaces around the =.

aws eks update-cluster-config \
   --name <cluster-name> \
   --upgrade-policy supportType=STANDARD

works as well and without needing quotation marks.

[geoffcline]

Hello! 👋

I've captured your suggested changes in our internal system as we prepare to migrate this repository from Markdown to AsciiDoc format. We'll be offline for about a week during this transition, so I'm closing this PR for housekeeping purposes.

Your contribution will be included when we republish with the new format. Thank you for helping improve our AWS documentation!