Bug 1531724 - Revert SupportUTF8 registry setting from bug 1521007. r=me

mail/installer/windows/nsis/shared.nsh

@@ -358,7 +358,7 @@
   WriteRegStr ${RegKey} "$0" "" "${ClientsRegName}"
   WriteRegStr ${RegKey} "$0\DefaultIcon" "" "$8,0"
   WriteRegStr ${RegKey} "$0" "DLLPath" "$6"
-  WriteRegDWORD ${RegKey} "$0" "SupportUTF8" 1
+  WriteRegDWORD ${RegKey} "$0" "SupportUTF8" 0
 
   ; The MapiProxy dll can exist in multiple installs of the application.
   ; Registration occurs as follows with the last action to occur being the one

suite/installer/windows/nsis/shared.nsh

@@ -467,7 +467,7 @@
   WriteRegStr HKLM "$0" "" "${BrandFullNameInternal}"
   WriteRegStr HKLM "$0\DefaultIcon" "" "$8,0"
   WriteRegStr HKLM "$0" "DLLPath" "$6"
-  WriteRegDWORD HKLM "$0" "SupportUTF8" 1
+  WriteRegDWORD HKLM "$0" "SupportUTF8" 0
 
   ; The MapiProxy dll can be used by multiple applications but
   ; is only registered for the last application installed. When the last