[editorial] Hugo front matter is missing from new configuration/sdk.md page

[chalin]

Originally posted by @chalin in #4128 (comment):

This Hugo front matter should have been moved to the top of the new sdk.md file, otherwise we lose the alias, which can result in 404s.

/cc @open-telemetry/docs-maintainers

This is what is missing:

<!--- Hugo front matter used to generate the website version of this page:
linkTitle: SDK
aliases: [/docs/reference/specification/sdk-configuration]
--->

And, now that the page has been renamed, we actually need a new alias (to be added to the aliases array):

• sdk-configuration

Reference:

• Define instrumentation configuration API #4128