bump mattermost to 6.0.0

(done as a seperate branch since it requires manual intervention; not
test-deployed since mediawiki fails to build again …)

nix/sources.json

@@ -23,19 +23,19 @@
         "homepage": "https://mattermost.com",
         "owner": "mattermost",
         "repo": "mattermost-server",
-        "rev": "ff10bf1068969a9d27ced26741a923a1b2962257",
-        "sha256": "0qcl32lidvwjrg8kil8a67141lnbrdx3hha0y9cwdlz8b6l8gxsz",
+        "rev": "c02cdd842a48d53b63fbb476e3af121645478562",
+        "sha256": "1w9s5kfpmhfh0d7wy0zvhax6cjrdgxms9gdzfla4zjc7r52hjf6b",
         "type": "tarball",
-        "url": "https://github.com/mattermost/mattermost-server/archive/refs/tags/v5.39.0.tar.gz",
+        "url": "https://github.com/mattermost/mattermost-server/archive/refs/tags/v6.0.0.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/refs/tags/v<version>.tar.gz",
-        "version": "5.39.0"
+        "version": "6.0.0"
     },
     "mattermost-webapp": {
-        "sha256": "1dm7zswz61p1008hkz0c4maq8382p8iv5kmc4ivzlqd2hhixbvvg",
+        "sha256": "1vncxgz3m7fzmalhpwpc2636yrjpsbqd8cjq7a3w2ckhqgdkzy9v",
         "type": "tarball",
-        "url": "https://releases.mattermost.com/5.39.0/mattermost-5.39.0-linux-amd64.tar.gz",
+        "url": "https://releases.mattermost.com/6.0.0/mattermost-6.0.0-linux-amd64.tar.gz",
         "url_template": "https://releases.mattermost.com/<version>/mattermost-<version>-linux-amd64.tar.gz",
-        "version": "5.39.0"
+        "version": "6.0.0"
     },
     "mumble-website": {
         "branch": "master",