Enable the default behavior of the geometry shader

Bug: angleproject:3571
Test: dEQP-GLES31.functional.geometry_shading.input.basic_primitive.points
      dEQP-GLES31.functional.geometry_shading.input.basic_primitive.lines
      dEQP-GLES31.functional.geometry_shading.input.basic_primitive.line_loop
      dEQP-GLES31.functional.geometry_shading.input.basic_primitive.line_strip
      dEQP-GLES31.functional.geometry_shading.input.basic_primitive.triangles
      dEQP-GLES31.functional.geometry_shading.input.basic_primitive.triangle_strip
      dEQP-GLES31.functional.geometry_shading.input.basic_primitive.triangle_fan
Change-Id: I65708d19bbfe6a0ad8ca392a1d6b3609b1410ef4
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1793753
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>