Allow glFramebufferTexture2D with level!=0 in ES2 tests with ES3

Allow glFramebufferTexture2D with level!=0 in ES2 tests with ES3

These ES2 tests were expecting GL errors when attaching non-zero
levels to a framebuffer where GL_OES_fbo_render_mipmap is not
supported. This functionality is core in ES3 contexts, so the tests
much assume support for mippmapped rendering in this case.

Affects:
dEQP-GLES2.functional.negative_api.buffer.framebuffer_texture2d
dEQP-GLES2.functional.fbo.api.texture_levels

Components:
dEQP

VK-GL-CTS issue: 1263

Change-Id: I3dc7c8f1f2cc7efb5c227a0aec11983b185be03c