chore(cli): fix test flake when running in coder workspace (coder#17604)

This test was failing inside a Coder workspace due to
`CODER_AGENT_TOKEN` being set.

Author: johnstcn

cli/exp_mcp_test.go

@@ -158,6 +158,7 @@ func TestExpMcpServer(t *testing.T) {
 //nolint:tparallel,paralleltest
 func TestExpMcpConfigureClaudeCode(t *testing.T) {
 	t.Run("NoReportTaskWhenNoAgentToken", func(t *testing.T) {
+		t.Setenv("CODER_AGENT_TOKEN", "")
 		ctx := testutil.Context(t, testutil.WaitShort)
 		cancelCtx, cancel := context.WithCancel(ctx)
 		t.Cleanup(cancel)