remove pointless copying from one set to another (#474)

just tidying up some more nonsense

Author: dimbleby

src/poetry/core/masonry/builders/builder.py

@@ -130,14 +130,8 @@ def find_excluded_files(self, fmt: str | None = None) -> set[str]:
                     )
 
             ignored = (vcs_ignored_files | explicitely_excluded) - explicitely_included
-            result = set()
-            for file in ignored:
-                result.add(file)
-
-            # The list of excluded files might be big and we will do a lot
-            # containment check (x in excluded).
-            # Returning a set make those tests much much faster.
-            self._excluded_files = result
+
+            self._excluded_files = ignored
 
         return self._excluded_files