[Tests] Fix resources-templates-read to return a resolved URI (#460)

The fixture returned the literal template pattern test://template/{id}/data
instead of substituting id, failing the wire-schema uri format check. Also
switches the json-schema-2020-12 baseline entry to a bare scenario name: the
latest (0.1.x) conformance CLI doesn't parse scenario:check-id syntax, only
alpha (0.2.x) does, and the two need to agree since conformance-weekly runs
2025-11-25 against latest while pipeline.yaml pins alpha.

Verified locally against both dist-tags and both spec revisions.

tests/Conformance/Elements.php

@@ -146,7 +146,7 @@ final class Elements
     public function resourceTemplate(string $id): TextResourceContents
     {
         return new TextResourceContents(
-            uri: 'test://template/{id}/data',
+            uri: \sprintf('test://template/%s/data', $id),
             mimeType: 'application/json',
             text: json_encode([
                 'id' => $id,