fix(deps): update dependency preact to v10.21.0 (cylc#1793)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -42,7 +42,7 @@
     "markdown-it": "14.1.0",
     "mitt": "3.0.1",
     "nprogress": "1.0.0-1",
-    "preact": "10.20.2",
+    "preact": "10.21.0",
     "subscriptions-transport-ws": "0.11.0",
     "svg-pan-zoom": "3.6.1",
     "vue": "3.4.11",

yarn.lock

@@ -3864,7 +3864,7 @@ __metadata:
     nodemon: "npm:3.1.0"
     nprogress: "npm:1.0.0-1"
     nyc: "npm:15.1.0"
-    preact: "npm:10.20.2"
+    preact: "npm:10.21.0"
     sass: "npm:1.75.0"
     sinon: "npm:17.0.2"
     standard: "npm:17.1.0"
@@ -8416,10 +8416,10 @@ __metadata:
   languageName: node
   linkType: hard
 
-"preact@npm:10.20.2":
-  version: 10.20.2
-  resolution: "preact@npm:10.20.2"
-  checksum: 10c0/e79c1e3ab0bab6a08dce157fc33a537487365a9093bcdc1a60612be8073a354e84648df9ee1eef5306b640461c99c9ef024720405e3e8219c03ed17e95de981e
+"preact@npm:10.21.0":
+  version: 10.21.0
+  resolution: "preact@npm:10.21.0"
+  checksum: 10c0/1f3cfcb5ca83b780b53593bcb917ae2e8d10a37405c32fb6774be1b5f1f3167d2156bd22c058627388330acc54da35fe8d4bbe7d38ae567a10e5d8fd943a1a06
   languageName: node
   linkType: hard