Reverts "[Impeller] support GLES 3.0 MSAA without extension. (#56705)"

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Reverts: #56705

Initiated by: jonahwilliams

Reason for reverting: goldens occassionally fail to render anything.

Original PR Author: jonahwilliams

Reviewed By: {gaaclarke}

This change reverts the following previous change:
Adds multisampling support for GLES devices without GL_EXT_multisampled_render_to_texture provided they are at least GLES 3.0 to support mutlisampled render buffers.

Fixes flutter/flutter#158360
Fixes flutter/flutter#157951

TBD: should we prefer renderbuffer 3.0 approach over multisample_render_to_texture?

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