Hoist @standard-schema/spec to the workspace root

The @standard-schema/spec import is shared by the fedify and testing
packages, so it belongs at the workspace level rather than being
declared per package.  The root deno.json already lists it and
workspace members inherit the root import map, making the copy in the
fedify package's deno.json redundant; drop it.  The pnpm side already
sources the version from the catalog in pnpm-workspace.yaml, with each
package.json referencing it as "catalog:".

Assisted-by: Claude Code:claude-fable-5

Author: 2chanhaeng

deno.lock

@@ -15,7 +15,6 @@
   },
   "imports": {
     "@multiformats/base-x": "npm:@multiformats/base-x@^4.0.1",
-    "@standard-schema/spec": "jsr:@standard-schema/spec@^1.1.0",
     "@std/assert": "jsr:@std/assert@^0.226.0",
     "@std/url": "jsr:@std/url@^0.225.1",
     "devalue": "npm:devalue@^5.8.1",