Updated pgvector on CI

Author: ankane

.github/workflows/build.yml

@@ -20,7 +20,7 @@ jobs:
           dev-files: true
       - run: |
           cd /tmp
-          git clone --branch v0.8.0 https://github.com/pgvector/pgvector.git
+          git clone --branch v0.8.1 https://github.com/pgvector/pgvector.git
           cd pgvector
           make
           sudo make install