Update nginx.conf (bazelbuild#2643)

Author: KarolinaKalin

slack-bazel-build/docker/nginx.conf

@@ -18,7 +18,7 @@ http {
         listen      ${PORT};
         server_name slack.bazel.build;
 
-        return 301 https://join.slack.com/t/bazelbuild/shared_invite/zt-3w1ecr78i-qn_sCHN3ik0xmyiSPOkg9g;
+        return 301 https://join.slack.com/t/bazelbuild/shared_invite/zt-3z03j6exf-6vQ3Hc2FC_~DnMqY00qrSA;
 
         error_page   500 502 503 504  /50x.html;
         location = /50x.html {