Fix typo

Author: Yuval Langer <[email protected]>

Closes pandas-dev#12523 from yuvallanger/patch-1 and squashes the following commits:

7e3f85b [Yuval Langer] Fix typo

Author: yuvallanger

doc/source/advanced.rst

@@ -281,7 +281,7 @@ As usual, **both sides** of the slicers are included as this is label indexing.
 .. warning::
 
    You should specify all axes in the ``.loc`` specifier, meaning the indexer for the **index** and
-   for the **columns**. Their are some ambiguous cases where the passed indexer could be mis-interpreted
+   for the **columns**. There are some ambiguous cases where the passed indexer could be mis-interpreted
    as indexing *both* axes, rather than into say the MuliIndex for the rows.
 
    You should do this: