D300: prevent autofix when both triples are in body (#8462)

## Summary
Addresses
#8402 (comment)

## Test Plan

Added associated test

Author: T-256

crates/ruff_linter/resources/test/fixtures/pydocstyle/D300.py

@@ -8,3 +8,19 @@ def ends_in_quote():
 
 def contains_quote():
     'Sum"\\mary.'
+
+
+# OK
+def contains_triples(t):
+    """('''|\""")"""
+
+
+# OK
+def contains_triples(t):
+    '''(\'''|""")'''
+
+
+# TODO: here should raise D300 for using dobule quotes instead,
+# because escaped double quote does allow us.
+def contains_triples(t):
+    '''(\""")'''

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

@@ -61,12 +61,14 @@ impl Violation for TripleSingleQuotes {
 pub(crate) fn triple_quotes(checker: &mut Checker, docstring: &Docstring) {
     let leading_quote = docstring.leading_quote();
 
-    let prefixes = docstring
-        .leading_quote()
+    let prefixes = leading_quote
         .trim_end_matches(|c| c == '\'' || c == '"')
         .to_owned();
 
     let expected_quote = if docstring.body().contains("\"\"\"") {
+        if docstring.body().contains("\'\'\'") {
+            return;
+        }
         Quote::Single
     } else {
         Quote::Double

crates/ruff_linter/src/rules/pydocstyle/snapshots/ruff_linter__rules__pydocstyle__tests__preview__D300_D300.py.snap

@@ -1,5 +1,6 @@
 ---
 source: crates/ruff_linter/src/rules/pydocstyle/mod.rs
+assertion_line: 134
 ---
 D300.py:6:5: D300 Use triple double quotes `"""`
   |
@@ -23,5 +24,8 @@ D300.py:10:5: D300 [*] Use triple double quotes `"""`
 9  9  | def contains_quote():
 10    |-    'Sum"\\mary.'
    10 |+    """Sum"\\mary."""
+11 11 | 
+12 12 | 
+13 13 | # OK