Fix e2e test failure by pinning modelcontextprotocol/inspector

[brianr]

Problem

When running the e2e test get-item-details:

Running: npx -y @modelcontextprotocol/inspector --cli -e ROLLBAR_ACCESS_TOKEN=$ROLLBAR_E2E_READ_TOKEN npx -y ./rollbar-mcp-server-0.2.3.tgz --method tools/call --tool-name get-item-details --tool-arg counter=8 --tool-arg max_tokens=100
✗ E2E test failed: Tool invocation returned an error
Response:
npm warn deprecated [email protected]: Use your platform's native DOMException instead
{
  "content": [

The test (rightly) fails because of the deprecation warning being printed. That happens because the latest version of @modelcontextprotocol/inspector depends (indirectly) on node-domexception, which is deprecated.

Solution

Pin @modelcontextprotocol/inspector to 0.16.2, via devDependencies.