LibGfx: Remove OpenType::Font::m_buffer

At first glance this looks like it holds the memory that the various
slices point into... but it actually doesn't own that memory. Nobody
uses m_buffer, so it serves no purpose.

Userland/Libraries/LibGfx/Font/OpenType/Font.cpp

@@ -278,7 +278,6 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
     }
 
     return adopt_ref(*new Font(
-        move(buffer),
         move(head),
         move(name),
         move(hhea),

Userland/Libraries/LibGfx/Font/OpenType/Font.h

@@ -82,7 +82,6 @@ private:
     static ErrorOr<NonnullRefPtr<Font>> try_load_from_offset(ReadonlyBytes, unsigned index = 0);
 
     Font(
-        ReadonlyBytes bytes,
         Head&& head,
         Name&& name,
         Hhea&& hhea,
@@ -98,8 +97,7 @@ private:
         Optional<CBLC> cblc,
         Optional<CBDT> cbdt,
         Optional<GPOS> gpos)
-        : m_buffer(move(bytes))
-        , m_head(move(head))
+        : m_head(move(head))
         , m_name(move(name))
         , m_hhea(move(hhea))
         , m_maxp(move(maxp))
@@ -119,8 +117,6 @@ private:
 
     RefPtr<Core::Resource> m_resource;
 
-    ReadonlyBytes m_buffer;
-
     // These are stateful wrappers around non-owning slices
     Head m_head;
     Name m_name;