[Enhancement] Using del in the drop(where inplace=True) is faster than the current drop method
#### Code Sample, a copy-pastable example if possible

```python
# Your code here
a = time()
df.drop('x',axis=1,inplace=True)
print(time()-a)#0.02...
#imagine we got the values of column x again...
a = time()
del df['x']
print(time()-a)#0.0009...

#the del method is faster to delete the column in place...
```
#### Problem description

I cant seem to locate the drop function anywhere or else I would commit it myself. What I am imagining is the drop would check if kwarg inplace is true, if it is, it would do something to drop the table, right? 
If I am right, then cant we just replace the something with del dataframe[column_name]? I am not an expert programmer like y'all, so please do correct me if I am wrong...Thank you

#### Expected Output

#### Output of ``pd.show_versions()``

<details>

0.23.0

</details>
