The string for VertexAttribType::HalfFloatOES was missing.  The output
would contain GL_INVALID_ENUM instead of GL_HALF_FLOAT_OES.

Detected when capturing Free Fire.

Test: Free Fire MEC
Bug: b/168049517
Bug: angleproject:4048
Change-Id: Ib9efbb8cee1ae9f679ff20f4182f7dd428000d5b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2461349
Commit-Queue: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>