ci: test against liblsl v1.18.0.b2 in CI workflow

Match the publish workflow so PR/push CI exercises the same beta
liblsl that the release bundles.

Author: cboulay

.github/workflows/ci.yml

@@ -9,8 +9,8 @@ on:
   workflow_dispatch:
 
 env:
-  LSL_RELEASE_URL: "https://github.com/sccn/liblsl/releases/download/v1.17.7"
-  LSL_RELEASE: "1.17.7"
+  LSL_RELEASE_URL: "https://github.com/sccn/liblsl/releases/download/v1.18.0.b2"
+  LSL_RELEASE: "1.18.0"
 
 jobs: