Fix: F999 dictionary key '2000q4' repeated with different values
Removal of duplicate line to fix lint error

```
pandas/tseries/tests/test_tslib.py:685:18: F999 dictionary key '2000q4' repeated with different values
pandas/tseries/tests/test_tslib.py:690:18: F999 dictionary key '2000q4' repeated with different values
```
