[class.gslice.overview] Replace $$...$$ with \[...\]. (#1334)

Author: Eelis

source/numerics.tex

@@ -8023,10 +8023,8 @@
 the
 \tcode{valarray}
 template, which is one-dimensional.
-The set of one-dimensional index values specified by a
-\tcode{gslice}
-are $$k = s + \sum_ji_jd_j$$
-% \$k = s + sum from j \{ i sub j d sub j \}\$
+The set of one-dimensional index values specified by a \tcode{gslice} are
+\[ k = s + \sum_j i_j d_j \]
 where the multidimensional indices $i_j$ range in value from
 0 to $l_{ij} - 1$.
 
@@ -8041,9 +8039,7 @@
 stride = {19, 4, 1}
 \end{codeblock}
 yields the sequence of one-dimensional indices
-
-$$k = 3 + (0,1) \times 19 + (0,1,2,3) \times 4 + (0,1,2) \times 1$$
-
+\[ k = 3 + (0, 1) \times 19 + (0, 1, 2, 3) \times 4 + (0, 1, 2) \times 1 \]
 which are ordered as shown in the following table:
 
 \begin{tabbing}