df.Truncate now fails when arguments have different tzinfo
#### Code Sample

```python
df = pd.DataFrame()
date1 = pd.Timestamp('20190101', tz='Europe/Brussels')
date2 = pd.Timestamp('20190201T00:00:00+01:00')
df.truncate(before=date1, after=date2)
```
```python
File "/python3.7/site-packages/pandas/core/indexes/base.py", line 5244, in slice_locs
    raise ValueError("Both dates must have the " "same UTC offset")
ValueError: Both dates must have the same UTC offset
```

#### Problem description

In #25263, these lines were added (line 4881):
```python
if not tz_compare(ts_start.tzinfo, ts_end.tzinfo):
    raise ValueError("Both dates must have the same UTC offset"
```

1. The timestamps in the example do have the same UTC offset. The difference is that one has an actual timezone, while the other has a fixed offset. So a simple comparison of `tzinfo` is insufficient here.
2. It is unclear to my *why* you shouldn't be able to truncate with timestamps with different offsets!?

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

<details>

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.3.final.0
python-bits      : 64
OS               : Darwin
OS-release       : 18.6.0
machine          : x86_64
processor        : i386
byteorder        : little
LC_ALL           : en_US.UTF-8
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8
pandas           : 0.25.3
numpy            : 1.16.4
pytz             : 2019.1
dateutil         : 2.8.0
pip              : 19.2.1
setuptools       : 28.8.0
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : 4.3.3
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : None
IPython          : None
pandas_datareader: None
bs4              : 4.7.1
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : 4.3.3
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : None
sqlalchemy       : 1.3.3
tables           : None
xarray           : None
xlrd             : 1.2.0
xlwt             : None
xlsxwriter       : None

</details>