Remove printQueryOpt.quote field.

This field was included in the original definition of the printQueryOpt
struct in commit a45195a191, but it was not used anywhere in that
commit, nor since then.  Spotted by Dickson S. Guedes.

src/bin/psql/print.h

@@ -152,7 +152,6 @@ typedef struct printQueryOpt
 {
 	printTableOpt topt;			/* the options above */
 	char	   *nullPrint;		/* how to print null entities */
-	bool		quote;			/* quote all values as much as possible */
 	char	   *title;			/* override title */
 	char	  **footers;		/* override footer (default is "(xx rows)") */
 	bool		translate_header;		/* do gettext on column headers */