DOC: Uniform block directive syntax.

block directive syntax technically does not have space before the
double-colon.

While this seem to be accepted by docutils – but not documented,
this can throw off other RST parser/syntax highlighter.
Sometime they can see that as comments, sometime they give garbage out.

Plus this is really uncommon with 3 occurrences in pandas codebase with
space and 4800 without:

    pandas[master]  $ rg '\.\. \w+::' | wc -l
    4853

Numpy and scipy used to have a few space in their block directive, but
current master/main branch of both should also be free of directive with
space before the double colon.

Author: Carreau

doc/source/user_guide/io.rst

@@ -3546,9 +3546,9 @@ with ``on_demand=True``.
 Specifying sheets
 +++++++++++++++++
 
-.. note :: The second argument is ``sheet_name``, not to be confused with ``ExcelFile.sheet_names``.
+.. note:: The second argument is ``sheet_name``, not to be confused with ``ExcelFile.sheet_names``.
 
-.. note :: An ExcelFile's attribute ``sheet_names`` provides access to a list of sheets.
+.. note:: An ExcelFile's attribute ``sheet_names`` provides access to a list of sheets.
 
 * The arguments ``sheet_name`` allows specifying the sheet or sheets to read.
 * The default value for ``sheet_name`` is 0, indicating to read the first sheet

pandas/core/algorithms.py

@@ -633,7 +633,7 @@ def factorize(
         is a Categorical. When `values` is some other pandas object, an
         `Index` is returned. Otherwise, a 1-D ndarray is returned.
 
-        .. note ::
+        .. note::
 
            Even if there's a missing value in `values`, `uniques` will
            *not* contain an entry for it.