Revert "enable multivalues insert (#19664)"
This reverts commit 7c7bd569ce8e0f117c618d068e3d2798134dbc73.

Reverts https://github.com/pandas-dev/pandas/pull/19664 
Closes https://github.com/pandas-dev/pandas/issues/21103
I didn't really know where to put this in the whatsnew file. Because as a revert it does not really fit in "bug fixes" IMO. 
Any ideas? (I now added it in a section "regressions") Regressions seems fine, unless you read it as "We've introduced these new regressions!" :) I can make the title "Fixed regressions" :-) # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21355?src=pr&el=h1) Report
> Merging [#21355](https://codecov.io/gh/pandas-dev/pandas/pull/21355?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/649bfae90f70e8ee7181aba31b0f0b44f09b76e6?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/21355/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/21355?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #21355   +/-   ##
=======================================
  Coverage   91.85%   91.85%           
=======================================
  Files         153      153           
  Lines       49564    49564           
=======================================
  Hits        45527    45527           
  Misses       4037     4037
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.25% <ø> (ø)` | :arrow_up: |
| #single | `41.86% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21355?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/21355?src=pr&el=footer). Last update [649bfae...22a6dcf](https://codecov.io/gh/pandas-dev/pandas/pull/21355?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
