DOC: fix some sphinx build issues (#14332)

* DOC: proper rst syntax for table

* DOC: fix 'Unexpected indentation'

* DOC: fix links to offset aliases

Author: jorisvandenbossche

doc/source/categorical.rst

@@ -757,12 +757,18 @@ Use ``.astype`` or ``union_categoricals`` to get ``category`` result.
 
 Following table summarizes the results of ``Categoricals`` related concatenations.
 
-| arg1         | arg2                                 | result  |
-|---------|-------------------------------------------|---------|
-| category | category (identical categories) | category |
-| category | category (different categories, both not ordered) | object (dtype is inferred) |
++----------+--------------------------------------------------------+----------------------------+
+| arg1     | arg2                                                   | result                     |
++==========+========================================================+============================+
+| category | category (identical categories)                        | category                   |
++----------+--------------------------------------------------------+----------------------------+
+| category | category (different categories, both not ordered)      | object (dtype is inferred) |
++----------+--------------------------------------------------------+----------------------------+
 | category | category (different categories, either one is ordered) | object (dtype is inferred) |
-| category | not category | object (dtype is inferred) |
++----------+--------------------------------------------------------+----------------------------+
+| category | not category                                           | object (dtype is inferred) |
++----------+--------------------------------------------------------+----------------------------+
+
 
 Getting Data In/Out
 -------------------

pandas/core/generic.py

@@ -3999,7 +3999,7 @@ def asfreq(self, freq, method=None, how=None, normalize=False):
         converted : type of caller
 
         To learn more about the frequency strings, please see `this link
-<http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases>`__.
+        <http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases>`__.
         """
         from pandas.tseries.resample import asfreq
         return asfreq(self, freq, method=method, how=how, normalize=normalize)

pandas/indexes/base.py

@@ -1994,7 +1994,7 @@ def symmetric_difference(self, other, result_name=None):
         ``symmetric_difference`` contains elements that appear in either
         ``idx1`` or ``idx2`` but not both. Equivalent to the Index created by
         ``idx1.difference(idx2) | idx2.difference(idx1)`` with duplicates
-         dropped.
+        dropped.
 
         Examples
         --------

pandas/tseries/index.py

@@ -196,6 +196,9 @@ class DatetimeIndex(DatelikeOps, TimelikeOps, DatetimeIndexOpsMixin,
     name : object
         Name to be stored in the index
 
+    Notes
+    -----
+
     To learn more about the frequency strings, please see `this link
     <http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases>`__.
     """

pandas/tseries/tdi.py

@@ -112,6 +112,9 @@ class TimedeltaIndex(DatetimeIndexOpsMixin, TimelikeOps, Int64Index):
     name : object
         Name to be stored in the index
 
+    Notes
+    -----
+
     To learn more about the frequency strings, please see `this link
     <http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases>`__.
     """