feat: create unregister shield API endpoint

docs/_static/llama-stack-spec.yaml

@@ -999,6 +999,31 @@ paths:
           required: true
           schema:
             type: string
+    delete:
+      responses:
+        '200':
+          description: OK
+        '400':
+          $ref: '#/components/responses/BadRequest400'
+        '429':
+          $ref: >-
+            #/components/responses/TooManyRequests429
+        '500':
+          $ref: >-
+            #/components/responses/InternalServerError500
+        default:
+          $ref: '#/components/responses/DefaultError'
+      tags:
+        - Shields
+      description: Unregister a shield.
+      parameters:
+        - name: identifier
+          in: path
+          description: >-
+            The identifier of the shield to unregister.
+          required: true
+          schema:
+            type: string
   /v1/telemetry/traces/{trace_id}/spans/{span_id}:
     get:
       responses: