fix(doc): update expired Slack invite links in README (#8739)

The Slack invite links in README.md were expired and returning
"This link is no longer active." Updated both occurrences (badge
and community section) to match the current link on the official
DevLake website.

Closes #8738

Co-authored-by: Spiff Azeta <spiffazeta@gmail.com>

Author: spiffaz

README.md

@@ -25,7 +25,7 @@ limitations under the License.
 [![Dockerhub pulls](https://img.shields.io/badge/dynamic/json?url=https%3A%2F%2Fhub.docker.com%2Fv2%2Frepositories%2Fapache%2Fdevlake&query=%24.pull_count&label=Dockerhub%20pulls)](https://hub.docker.com/r/apache/devlake)
 [![unit-test](https://github.com/apache/incubator-devlake/actions/workflows/test.yml/badge.svg)](https://github.com/apache/incubator-devlake/actions/workflows/test.yml)
 [![Go Report Card](https://goreportcard.com/badge/github.com/apache/incubator-devlake)](https://goreportcard.com/report/github.com/apache/incubator-devlake)
-[![Slack](https://img.shields.io/badge/slack-join_chat-success.svg?logo=slack)](https://join.slack.com/t/devlake-io/shared_invite/zt-18uayb6ut-cHOjiYcBwERQ8VVPZ9cQQw)
+[![Slack](https://img.shields.io/badge/slack-join_chat-success.svg?logo=slack)](https://join.slack.com/t/devlake-io/shared_invite/zt-1lkgbdmys-AU2azidzO1u~mtjlg9my7A)
 [![Twitter](https://badgen.net/badge/icon/twitter?icon=twitter&label)](https://twitter.com/ApacheDevLake)
 
 </div>
@@ -121,7 +121,7 @@ One of the best ways to get started contributing is by improving DevLake's docum
 
 ## 💙 Community
 
-Message us on <a href="https://join.slack.com/t/devlake-io/shared_invite/zt-18uayb6ut-cHOjiYcBwERQ8VVPZ9cQQw" target="_blank">Slack</a>
+Message us on <a href="https://join.slack.com/t/devlake-io/shared_invite/zt-1lkgbdmys-AU2azidzO1u~mtjlg9my7A" target="_blank">Slack</a>
 
 ## 📄 License<a id="license"></a>