colormanager: temporarily hardcoding default input color space

The first input color space is "linear" which is very rare for footage to be
in. For simplicity, it'll default to sRGB for now.

app/render/colormanager.cpp

@@ -37,8 +37,8 @@ ColorManager::ColorManager()
   // Ensures config is set to something
   config_ = OCIO::GetCurrentConfig();
 
-  // Default input space is first in config
-  default_input_color_space_ = ListAvailableInputColorspaces().first();
+  // Default input space
+  default_input_color_space_ = QStringLiteral("sRGB OETF");
 
   // Default reference space is scene linear
   reference_space_ = OCIO::ROLE_SCENE_LINEAR;