color-management: make (ext_)srgb aliases for gamma22

src/cmm/cmm_manager.rs

@@ -63,7 +63,7 @@ impl ColorManager {
             Some(NamedPrimaries::Srgb),
             Primaries::SRGB,
             Luminance::SRGB,
-            TransferFunction::Srgb,
+            TransferFunction::Gamma22,
             Primaries::SRGB,
             Luminance::SRGB.to_target(),
             None,

src/cmm/cmm_transfer_function.rs

@@ -2,14 +2,12 @@ use linearize::Linearize;
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Linearize)]
 pub enum TransferFunction {
-    Srgb,
     Linear,
     St2084Pq,
     Bt1886,
     Gamma22,
     Gamma28,
     St240,
-    ExtSrgb,
     Log100,
     Log316,
     St428,