Fix Kramdown Warnings in GraphQL documentation

The monthly documentation maintenance tasks identified a syntax error (Kramdown warning) in the GraphQL documentation.

Problem to solve

The Kramdown warning message is:

kramdown warning(s) for <Nanoc::Core::CompilationItemRepView item.identifier=/ee/api/graphql/reference/index.md name=default>
2062  No link definition for link ID '`production`' found on line 1

This seems to match line 11126 in index.md:

| <a id="dorametricsenvironmenttiers"></a>`environmentTiers` | [`[DeploymentTier!]`](#deploymenttier) | Deployment tiers of the environments to return. Defaults to [`PRODUCTION`]. |

Proposal

Edit the GraphQL source ee.app/graphql/resolvers/dora_metrics_resolver.rb line 34 to fix the syntax error.

The possible fix:

description: 'Deployment tiers of the environments to return. Defaults to `[PRODUCTION]`.'

Other links/references

technical-writing#639