Fix release binary

Author: dgehriger

.github/workflows/build.yml

@@ -71,8 +71,7 @@ jobs:
         run: |
           mkdir -p release
           cp mathjax/target/*.jar release/
-          server_bin=$(find mathjax-server/target -maxdepth 1 -type f -name "mathjax-server")
-          cp $server_bin release/
+          cp mathjax-server/target/x86_64-unknown-linux-gnu/release/mathjax-server release/
           zip -j "release/confluence-mathjax-plugin-${GITHUB_REF_NAME}.zip" release/*
 
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