Fix trailing kwargs end of line comment after slash (#10297)

## Summary

Fixes the handling end of line comments that belong to `**kwargs` when
the `**kwargs` come after a slash.

The issue was that we missed to include the `**kwargs` start position
when determining the start of the next node coming after the `/`.

Fixes https://github.com/astral-sh/ruff/issues/10281

## Test Plan

Added test

crates/ruff_python_formatter/tests/snapshots/format@statement__function.py.snap

@@ -284,6 +284,13 @@ def f42(
 ):
     pass
 
+# Regression test for https://github.com/astral-sh/ruff/issues/10281
+def f43(
+    __bar: str,
+    /,
+    **specifiers: typing.Any,  # noqa: ANN401
+) -> int:
+    return len(specifiers)
 
 # Check trailing commas are permitted in funcdef argument list.
 def f(a, ): pass
@@ -760,6 +767,15 @@ def f42(
     pass
 
 
+# Regression test for https://github.com/astral-sh/ruff/issues/10281
+def f43(
+    __bar: str,
+    /,
+    **specifiers: typing.Any,  # noqa: ANN401
+) -> int:
+    return len(specifiers)
+
+
 # Check trailing commas are permitted in funcdef argument list.
 def f(
     a,
@@ -999,6 +1015,3 @@ def function_with_one_argument_and_a_keyword_separator(
 ) -> ReallyReallyReallyReallyReallyReallyReallyReallyLongName:
     pass
 ```
-
-
-