Fix typo in lucicfg README
Fix typo in lucicfg README

Change-Id: I27da41aead8f73114ccf306abb306a98b8ddadc6
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2893991
Auto-Submit: Rob Mohr <d07614a8a0b466db08f68224f87d738b0f9615cf@google.com>
Commit-Queue: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@google.com>
Reviewed-by: Yiwei Zhang <50b2a565e2e78c292794832469a30ce5abc9959c@google.com>
Reviewed-by: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@google.com>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go