imath: Remove uneeded llvm dep

It's been here from first time the package was imported but it doesn't seem to be used.

imath.yaml

@@ -18,7 +18,6 @@ environment:
       - ca-certificates-bundle
       - cmake
       - doxygen
-      - llvm-18-dev
       - numpy
       - openssf-compiler-options
       - python3-dev
@@ -57,6 +56,11 @@ subpackages:
           mkdir -p ${{targets.subpkgdir}}/usr/lib/
           mv "${{targets.destdir}}"/usr/lib/python3* "${{targets.subpkgdir}}"/usr/lib/
           mv "${{targets.destdir}}"/usr/lib/libPy* "${{targets.subpkgdir}}"/usr/lib/
+    test:
+      pipeline:
+        - uses: python/import
+          with:
+            import: imath
 
 update:
   enabled: true