fix: posonlyargs missing comma in function def

Author: jvllmr

src/unparser.rs

@@ -1189,7 +1189,7 @@ impl Unparser {
                 || kw_iter.peek().is_some()
                 || node.kwarg.is_some()
             {
-                self.write_str(", / ");
+                self.write_str(", /, ");
             }
         }
 

test_files/function_def.py

@@ -0,0 +1,22 @@
+def name_4[*name_2](  # type: ignore
+    name_2,
+    /,
+    name_4,
+    name_1,
+    *name_0: str,
+    name_3: str = "",
+    name_5: str = "",
+) -> str:
+    return ""
+
+
+async def name_5[*name_2](  # type: ignore
+    name_2,
+    /,
+    name_4,
+    name_1,
+    *name_0: str,
+    name_3: str = "",
+    name_5: str = "",
+) -> str:
+    return ""