[wald*] adjust rst whitespace+spacing in preparation for myst conversion

This PR fixes white space to conform to rst specification in preparation for myst conversion.

This PR should not change anything on the html site.

[x] will need to fix a bug for quoteblock parsing and math for the following test case in sphinx-tomyst

Let's listen to Wald longer:

    As a basis for choosing among critical regions the following
    considerations have been advanced by Neyman and Pearson: In accepting
    or rejecting :math:`H_0` we may commit errors of two kinds. We commit
    an error of the first kind if we reject :math:`H_0` when it is true;
    we commit an error of the second kind if we accept :math:`H_0` when
    :math:`H_1` is true. After a particular critical region :math:`W` has
    been chosen, the probability of committing an error of the first
    kind, as well as the probability of committing an error of the second
    kind is uniquely determined. The probability of committing an error
    of the first kind is equal to the probability, determined by the
    assumption that :math:`H_0` is true, that the observed sample will be
    included in the critical region :math:`W`. The probability of
    committing an error of the second kind is equal to the probability,
    determined on the assumption that :math:`H_1` is true, that the
    probability will fall outside the critical region :math:`W`. For any
    given critical region :math:`W` we shall denote the probability of an
    error of the first kind by :math:`\alpha` and the probability of an
    error of the second kind by :math:`\beta`.

QuantEcon / lecture-python

[wald*] adjust rst whitespace+spacing in preparation for myst conversion #259