Remove OpenGL ES support

Remove the following:
 - Relevant backend kernels
 - Relevant backend functions
 - Relevant backend validation tests
 - Relevant backend specific examples
 - Remove backend support from Graph API
 - Remove backend support from build system

Update documentation

Resolves: COMPMID-4149

Change-Id: Id0621d6ee35169754de458103907aaba4ef770c0
Signed-off-by: Manuel Bottini <manuel.bottini@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/5097
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
diff --git a/tests/framework/ParametersLibrary.h b/tests/framework/ParametersLibrary.h
index 064b5ed..d367772 100644
--- a/tests/framework/ParametersLibrary.h
+++ b/tests/framework/ParametersLibrary.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019 Arm Limited.
+ * Copyright (c) 2019-2021 Arm Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -30,10 +30,6 @@
 #include "arm_compute/runtime/CL/CLRuntimeContext.h"
 #include "arm_compute/runtime/CL/CLTensor.h"
 #endif /* ARM_COMPUTE_CL */
-#ifdef ARM_COMPUTE_GC
-#include "arm_compute/runtime/GLES_COMPUTE/GCRuntimeContext.h"
-#include "arm_compute/runtime/GLES_COMPUTE/GCTensor.h"
-#endif /* ARM_COMPUTE_GC */
 
 #include <memory>
 
@@ -61,14 +57,6 @@
 };
 #endif /* ARM_COMPUTE_CL */
 
-#ifdef ARM_COMPUTE_GC
-template <>
-struct ContextType<GCTensor>
-{
-    using type = GCRuntimeContext;
-};
-#endif /* ARM_COMPUTE_GC */
-
 /** Class that contains all the global parameters used by the tests */
 class ParametersLibrary final
 {