CLN: ASV panel ctor
There were two benchmarks that were essentially the same (dictionary of dataframes with the same index benchmark), so I removed one along with the usual flake8.
```
$ asv dev -b ^panel_ctor
· Discovering benchmarks
· Running 3 total benchmarks (1 commits * 1 environments * 3 benchmarks)
[  0.00%] ·· Building for existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[  0.00%] ·· Benchmarking existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[ 33.33%] ··· Running panel_ctor.DifferentIndexes.time_from_dict          387ms
[ 66.67%] ··· Running panel_ctor.SameIndexes.time_from_dict              32.0ms
[100.00%] ··· Running panel_ctor.TwoIndexes.time_from_dict                105ms
```
