Remove backport from optionalDependencies

[shinebayar-g]

Description of the bug:

Package called backport is defined in the optionalDependencies. If I'm understanding correctly packages defined in optionalDependencies is installed by default. Thus considered as a direct dependency and its dependencies are getting flagged in security vulnerability. (Like axios for example).

cdk8s-core/package.json

Lines 174 to 176 in bc6f483

	"optionalDependencies": {
	"backport": "8.5.0"
	},

This is confirmed in npm as well.

I suggest we should move this to devDependencies.

Reproduction Steps:

Error Log:

Environment:

• Framework Version:
• OS:

Other:

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This is 🐛 Bug Report

[iliapolo]

Oh nice. We we should move it to devDependencies for sure. It used to be there, but it required a node version bump in all our workflows (because backport has higher node requirements than cdk8s) - but this makes it worth it.

Thanks!