docs typo fix

doc/background.rst

@@ -126,7 +126,7 @@ Fourier transform of :math:`\eqref{dlrexp}` yields
 
 .. math::
   \begin{equation}
-    G(i nu_n) \approx \sum_{l=1}^r K(i \nu_n,\omega_l) \widehat{g}_l, \label{dlrexp_imfreq} \tag{2}
+    G(i \nu_n) \approx \sum_{l=1}^r K(i \nu_n,\omega_l) \widehat{g}_l, \label{dlrexp_imfreq} \tag{2}
   \end{equation}
 
 so we see that the DLR expansion can be evaluated directly in imaginary time or
@@ -267,4 +267,4 @@ containing the point :math:`i \nu_n = 0` must have an odd number of points.
 Since it is undesirable to disallow this point, and to make sure all grids have
 the same number :math:`r` of points, we force :math:`r` to be odd. This requires
 including in each grid, by hand, a single point of high symmetry, and then allowing the
-pivoted Gram-Schmidt procedure to select the rest of the points symmetrically.
+pivoted Gram-Schmidt procedure to select the rest of the points symmetrically.