Don't trim last empty line in docstrings (#9813)

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

@@ -0,0 +1,125 @@
+---
+source: crates/ruff_python_formatter/tests/fixtures.rs
+input_file: crates/ruff_python_formatter/resources/test/fixtures/ruff/docstring_newlines.py
+---
+## Input
+```python
+# Tests that Ruff correctly preserves newlines before the closing quote
+
+def test():
+    """a, b
+c"""
+
+
+def test2():
+    """a, b
+    c
+"""
+
+def test3():
+    """a, b
+
+"""
+
+
+def test4():
+    """
+    a, b
+
+"""
+
+
+def test5():
+    """
+    a, b
+a"""
+
+def test6():
+    """
+    a, b
+
+    c
+"""
+
+
+
+def test7():
+    """
+    a, b
+
+
+
+
+"""
+
+def test7():
+    """
+    a, b
+
+
+
+    """
+```
+
+## Output
+```python
+# Tests that Ruff correctly preserves newlines before the closing quote
+
+
+def test():
+    """a, b
+    c"""
+
+
+def test2():
+    """a, b
+    c
+    """
+
+
+def test3():
+    """a, b"""
+
+
+def test4():
+    """
+    a, b
+
+    """
+
+
+def test5():
+    """
+        a, b
+    a"""
+
+
+def test6():
+    """
+    a, b
+
+    c
+    """
+
+
+def test7():
+    """
+    a, b
+
+
+
+
+    """
+
+
+def test7():
+    """
+    a, b
+
+
+
+    """
+```
+
+
+