fix: pure Python packages not building due to ubuntu-latest check

The build workflow was checking for matrix.os == 'ubuntu-latest',
but we changed the matrix to use 'ubuntu-22.04', causing the
pure Python packages (leann-core and leann) to never be built.

Changed to use pattern matching [[ == ubuntu-* ]] to match any
Ubuntu version.

This explains why v0.1.9 only published the C++ backend packages
but not the pure Python packages.

.github/workflows/build-reusable.yml

@@ -82,7 +82,7 @@ jobs:
       - name: Build packages
         run: |
           # Build core (platform independent)
-          if [ "${{ matrix.os }}" == "ubuntu-latest" ]; then
+          if [[ "${{ matrix.os }}" == ubuntu-* ]]; then
             cd packages/leann-core
             uv build
             cd ../..
@@ -107,7 +107,7 @@ jobs:
           cd ../..
           
           # Build meta package (platform independent)
-          if [ "${{ matrix.os }}" == "ubuntu-latest" ]; then
+          if [[ "${{ matrix.os }}" == ubuntu-* ]]; then
             cd packages/leann
             uv build
             cd ../..