correct a double-quote

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,7 @@
+2018-03-14  Dirk Eddelbuettel  <[email protected]>
+
+        * vignettes/Rcpp-FAQ.Rmd: Correct a double-quote (thanks, Joris Meys)
+
 2018-03-08  Dirk Eddelbuettel  <[email protected]>
 
         * DESCRIPTION: Release 0.12.16

vignettes/Rcpp-FAQ.Rmd

@@ -1403,7 +1403,7 @@ b
 With this being said, there is one last area of contention with the proxy model:
 the keyword `const`. The `const` declaration indicates that an object
 is not allowed to be modified by any action. Due to the way the proxy
-model paradigm works, there is a way to ``override'' the `const` designation.
+model paradigm works, there is a way to "override" the `const` designation.
 Simply put, one can create a new \pkg{Rcpp} object without the `const`
 declaration from a pre-existing one. As a result, the new \pkg{Rcpp} object
 would be allowed to be modified by the compiler and, thus, modifying the initial