fix: fixup polars join version check throwing unnecessary deprecation warning for outer join (#2287)

fixup polars join version check

Author: MarcoGorelli

narwhals/_polars/dataframe.py

@@ -426,7 +426,7 @@ def join(
         suffix: str,
     ) -> Self:
         how_native = (
-            "outer" if (self._backend_version < (1, 0, 0) and how == "full") else how
+            "outer" if (self._backend_version < (0, 20, 29) and how == "full") else how
         )
 
         try:
@@ -651,7 +651,7 @@ def join(
         suffix: str,
     ) -> Self:
         how_native = (
-            "outer" if (self._backend_version < (1, 0, 0) and how == "full") else how
+            "outer" if (self._backend_version < (0, 20, 29) and how == "full") else how
         )
 
         return self._from_native_frame(