[docs] [issue25866] Reference 3. Data Model: miscellaneous minor cleanups on the word "sequence".

Change by miss-islington <mariatta.wijaya+miss-islington@gmail.com>: ---------- pull_requests: +16713 pull_request: https://github.com/python/cpython/pull/17208 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue25866> _______________________________________