Convert quotes to TeX quotes

Co-authored-by: Henri Menke <[email protected]>

doc/generic/pgf/text-en/pgfmanual-en-tikz-matrices.tex

@@ -478,7 +478,7 @@ \subsubsection{Cell Styles and Options}
 In some cases, it is desirable to include some automation in each column/row
 separately. A typical example is to apply stripe-pattern to almost all columns
 and treat only a few of them differently. Then, nesting these keys can open up
-a lot of possibilities; in the following example a "feature comparison" table
+a lot of possibilities; in the following example a ``feature comparison'' table
 is demonstrated. It is intentionally made rather verbose to show how the column
 and row settings can be progressively overwritten to create certain effects.