update toolchain docker image version

Author: qno

.github/workflows/build-plugin.yml

@@ -2,7 +2,7 @@ name: Build VCV Rack Plugin
 on: [push, pull_request]
 
 env:
-  rack-sdk-version: 2.0.6
+  rack-sdk-version: 2.1.2
   rack-plugin-toolchain-dir: /home/build/rack-plugin-toolchain
 
 defaults:
@@ -34,7 +34,7 @@ jobs:
     needs: modify-plugin-version
     runs-on: ubuntu-latest
     container:
-      image: ghcr.io/qno/rack-plugin-toolchain-win-linux:v2
+      image: ghcr.io/qno/rack-plugin-toolchain-win-linux
       options: --user root
     strategy:
       matrix: