BUG: Use total_tie_count to normalize dense ranking
- [x] closes #18296
- [ ] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

As reported in #18296, for a `Series` with repeated values, `Series.rank(pct=True, method='dense').max()` may not be `<=1` as expected.

This is due to the division of the ranks by the total number of elements in the `Series`, instead of the maximum rank assigned. Here we update the calculation.
I've confirmed that the updated code gives the expected result from the example in #18296.  # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18297?src=pr&el=h1) Report
> Merging [#18297](https://codecov.io/gh/pandas-dev/pandas/pull/18297?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/148ed63f9287cc55f7a2802da300b717d01cabe6?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18297/graphs/tree.svg?token=eZ4WkYLtcO&width=650&src=pr&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/18297?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18297      +/-   ##
==========================================
- Coverage    91.4%   91.38%   -0.02%     
==========================================
  Files         164      164              
  Lines       49880    49880              
==========================================
- Hits        45592    45583       -9     
- Misses       4288     4297       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.19% <ø> (ø)` | :arrow_up: |
| #single | `39.42% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18297?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18297?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18297?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.8% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18297?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18297?src=pr&el=footer). Last update [148ed63...b7a81a9](https://codecov.io/gh/pandas-dev/pandas/pull/18297?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 how about some tests see #15630 (and linked PR soln but has comments). closing as stale. ping if you want to update.