Specify a valid semver range for extensions package (#944)

Author: JakeSCahill

package-lock.json

@@ -15,7 +15,7 @@
     "@antora/cli": "3.1.2",
     "@antora/site-generator": "3.1.2",
     "@asciidoctor/tabs": "^1.0.0-beta.5",
-    "@redpanda-data/docs-extensions-and-macros": "latest"
+    "@redpanda-data/docs-extensions-and-macros": "^3.0.0"
   },
   "devDependencies": {
     "@octokit/rest": "^21.0.1",