[pydocstyle] Fix D413 infinite loop for parenthesized docstring (#18930)

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## Summary

<!-- What's the purpose of the change? What does it do, and why? -->

Fixes #18908

crates/ruff_linter/resources/test/fixtures/pydocstyle/D413.py

@@ -69,3 +69,11 @@ def func():
     Returns:
         the value
         """
+
+
+def func():
+    ("""Docstring.
+
+    Raises:
+        ValueError: An error.
+    """)

crates/ruff_linter/src/rules/pydocstyle/rules/sections.rs

@@ -1717,7 +1717,7 @@ fn common_section(
                     format!(
                         "{}{}",
                         line_end.repeat(2 - num_blank_lines),
-                        docstring.compute_indentation()
+                        leading_space(docstring.compute_indentation())
                     ),
                     context.end() - del_len,
                     context.end(),

crates/ruff_linter/src/rules/pydocstyle/snapshots/ruff_linter__rules__pydocstyle__tests__D413_D413.py.snap

@@ -79,5 +79,27 @@ D413.py:69:5: D413 [*] Missing blank line after last section ("Returns")
 69 69 |     Returns:
 70 70 |         the value
 71    |-        """
-   71 |+
+72 71 | 
    72 |+    """
+   73 |+
+73 74 | 
+74 75 | def func():
+75 76 |     ("""Docstring.
+
+D413.py:77:5: D413 [*] Missing blank line after last section ("Raises")
+   |
+75 |     ("""Docstring.
+76 |
+77 |     Raises:
+   |     ^^^^^^ D413
+78 |         ValueError: An error.
+79 |     """)
+   |
+   = help: Add blank line after "Raises"
+
+ℹ Safe fix
+76 76 | 
+77 77 |     Raises:
+78 78 |         ValueError: An error.
+   79 |+
+79 80 |     """)