Align parsing of CRLF-terminated patterns

`\r\n` was parsed as a separate TextElement of `\n`, whereas `\n` is
parsed as part of the antecedent TextElement.

Author: RumovZ

fluent-syntax/src/parser/pattern.rs

@@ -174,8 +174,8 @@ where
                 b'\r' if self.is_byte_at(b'\n', self.ptr + 1) => {
                     self.ptr += 1;
                     return Ok((
-                        start_pos,
-                        self.ptr - 1,
+                        start_pos + 1,
+                        self.ptr,
                         text_element_type,
                         TextElementTermination::Crlf,
                     ));