[cleanup] Drop |kNone| from AdvancedCapability::Type

The advanced capabilities used by ChromeOS printing never make use of
the |kNone| capability type.

Bug: 809738
Change-Id: I27b0cdba58fa2ad2c4d803cf63ab2bf32dc15556
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2404475
Commit-Queue: Alan Screen <awscreen@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806028}

printing/backend/print_backend.h

@@ -62,7 +62,7 @@ struct PRINTING_EXPORT AdvancedCapability {
   AdvancedCapability(const AdvancedCapability& other);
   ~AdvancedCapability();
 
-  enum class Type : uint8_t { kNone = 0, kBoolean, kFloat, kInteger, kString };
+  enum class Type : uint8_t { kBoolean, kFloat, kInteger, kString };
 
   // IPP identifier of the attribute.
   std::string name;