insights: Fix license check for freezing insights

Created by: CristinaBirkel

Description

This is a bug fix for the license check. Previously I was using licensing.GetConfiguredProductLicenseInfo() and checking the plan's features for code-insights. For the real license I generated for k8s, this didn't pick up on the code-insights tag. (It did for the dev license I was using to test with locally though, which is why I had originally thought it was working.)

So this fix is to use licensing.Check(licensing.FeatureCodeInsights) instead, which is working with a license generated with all the tags I used for the k8s license.

More info on licenses here.

Test plan

Follow the same steps as in https://github.com/sourcegraph/sourcegraph/pull/32418 except that the license should be generated as follows:

go run ./enterprise/internal/license/generate-license.go -private-key ../dev-private/enterprise/dev/test-license-generation-key.pem -tags=plan:enterprise-0,acls,private-extension-registry,remote-extensions-allow-disallow,monitoring,true-up,batch-changes,code-insights,distro,internal -users=10 -expires=8784h