DOC: Edited docstring of Interval
The docstring contained a repeated segment, which I removed.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25410?src=pr&el=h1) Report
> Merging [#25410](https://codecov.io/gh/pandas-dev/pandas/pull/25410?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9c0f6a8d703b6bee48918f2c5d16418a7ff736e3?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/25410/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25410?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #25410   +/-   ##
=======================================
  Coverage   91.73%   91.73%           
=======================================
  Files         173      173           
  Lines       52845    52845           
=======================================
  Hits        48479    48479           
  Misses       4366     4366
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.3% <ø> (ø)` | :arrow_up: |
| #single | `41.73% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25410?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/25410?src=pr&el=footer). Last update [9c0f6a8...57aad68](https://codecov.io/gh/pandas-dev/pandas/pull/25410?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25410?src=pr&el=h1) Report
> Merging [#25410](https://codecov.io/gh/pandas-dev/pandas/pull/25410?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9c0f6a8d703b6bee48918f2c5d16418a7ff736e3?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/25410/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25410?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #25410   +/-   ##
=======================================
  Coverage   91.73%   91.73%           
=======================================
  Files         173      173           
  Lines       52845    52845           
=======================================
  Hits        48479    48479           
  Misses       4366     4366
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.3% <ø> (ø)` | :arrow_up: |
| #single | `41.73% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25410?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/25410?src=pr&el=footer). Last update [9c0f6a8...57aad68](https://codecov.io/gh/pandas-dev/pandas/pull/25410?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Thanks!