ci: pin Deno to 2.6.5 due to assert regression in 2.6.6

Refs: denoland/deno#31931
Refs: denoland/deno#31821 (comment)

Author: ChALkeR

.github/workflows/test.yml

@@ -170,7 +170,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        deno-version: ['v2.x']
+        deno-version: ['v2.6.5']
     steps:
       - uses: actions/checkout@a5ac7e51b41094c92402da3b24376905380afc29
       - uses: pnpm/action-setup@a7487c7e89a18df4991f7f222e4898a00d66ddda