Remove legacy renderer from source, build files and CI (#3384)

src/mbgl/gl/renderer_backend.cpp

@@ -7,9 +7,7 @@
 #include <mbgl/util/instrumentation.hpp>
 #include <mbgl/util/logging.hpp>
 
-#if MLN_DRAWABLE_RENDERER
 #include <mbgl/shaders/gl/shader_group_gl.hpp>
-#endif
 
 #include <cassert>
 
@@ -92,7 +90,6 @@ void RendererBackend::setScissorTest(bool enabled) {
 
 RendererBackend::~RendererBackend() = default;
 
-#if MLN_DRAWABLE_RENDERER
 /// @brief Register a list of types with a shader registry instance
 /// @tparam ...ShaderID Pack of BuiltIn:: shader IDs
 /// @param registry A shader registry instance
@@ -150,7 +147,6 @@ void RendererBackend::initShaders(gfx::ShaderRegistry& shaders, const ProgramPar
                   shaders::BuiltIn::SymbolSDFIconShader,
                   shaders::BuiltIn::SymbolTextAndIconShader>(shaders, programParameters);
 }
-#endif
 
 } // namespace gl
 } // namespace mbgl