pyqt-3d: simplify the formula

Formula/pyqt-3d.rb

@@ -21,17 +21,17 @@ class Pyqt3d < Formula
 
   def install
     pyqt = Formula["pyqt"]
-    xy = Language::Python.major_minor_version Formula["python@3.9"].opt_bin/"python3"
+    python = Formula["python@3.9"]
+    site_packages = Language::Python.site_packages(python)
 
     open("pyproject.toml", "a") do |f|
       f.puts <<~EOS
         [tool.sip.project]
-        sip-include-dirs = ["#{pyqt.opt_lib}/python#{xy}/site-packages/PyQt#{pyqt.version.major}/bindings"]
+        sip-include-dirs = ["#{pyqt.prefix/site_packages}/PyQt#{pyqt.version.major}/bindings"]
       EOS
     end
 
-    system "sip-install", "--target-dir", prefix
-    (lib/"python#{xy}/site-packages").install %W[#{prefix}/PyQt#{pyqt.version.major} #{prefix}/PyQt#{pyqt.version.major}_3D-#{version}.dist-info]
+    system "sip-install", "--target-dir", prefix/site_packages
   end
 
   test do