Bug 1225918 - avoid quoting MOZ_APP_DISPLAYNAME when used as a DEFINE; r=mshal

Moving DEFINES from Makefile.in to moz.build in
browser/installer/windows/ kept the single quotes for
MOZ_APP_DISPLAYNAME.  Unfortunately, the patch author missed that those
quotes were there for the shell's benefit, not as a part of the defined
value.  These extraneous quotes look rather unbecoming in the installer.

Since mozbuild adds the appropriate quoting to a defined value, we can
simply forego the quoting in the moz.build file.

browser/installer/windows/moz.build

@@ -7,5 +7,5 @@
 DEFINES['APP_VERSION'] = CONFIG['FIREFOX_VERSION']
 
 DEFINES['MOZ_APP_NAME'] = CONFIG['MOZ_APP_NAME']
-DEFINES['MOZ_APP_DISPLAYNAME'] = "'%s'" % CONFIG['MOZ_APP_DISPLAYNAME']
+DEFINES['MOZ_APP_DISPLAYNAME'] = CONFIG['MOZ_APP_DISPLAYNAME']
 DEFINES['MOZILLA_VERSION'] = CONFIG['MOZILLA_VERSION']