[syntax-errors] Raise unsupported syntax error for template strings prior to Python 3.14 (#18664)

Closes #18662

One question is whether we would like the range to exclude the quotes?

crates/ruff_python_parser/src/parser/expression.rs

@@ -1250,10 +1250,30 @@ impl<'src> Parser<'src> {
                         .into(),
                 ));
             } else if self.at(TokenKind::TStringStart) {
-                strings.push(StringType::TString(
+                // test_ok template_strings_py314
+                // # parse_options: {"target-version": "3.14"}
+                // t"{hey}"
+                // t'{there}'
+                // t"""what's
+                // happening?"""
+                // "implicitly"t"concatenated"
+
+                // test_err template_strings_py313
+                // # parse_options: {"target-version": "3.13"}
+                // t"{hey}"
+                // t'{there}'
+                // t"""what's
+                // happening?"""
+                // "implicitly"t"concatenated"
+                let string_type = StringType::TString(
                     self.parse_interpolated_string(InterpolatedStringKind::TString)
                         .into(),
-                ));
+                );
+                self.add_unsupported_syntax_error(
+                    UnsupportedSyntaxErrorKind::TemplateStrings,
+                    string_type.range(),
+                );
+                strings.push(string_type);
             }
         }