SpecializeShader should require compatible Execution Model, not ExecutionMode #89

In the document The OpenGL® Graphics System: A Specification (Version 4.6 (Core Profile) - May 5, 2022), section 7.2.1 Shader Specialization, the error listing reads:

An INVALID_OPERATION error is generated if the ExecutionMode of the OpEntryPoint indicated by pEntryPoint does not match the type of shader.

This should be Execution Model, not ExecutionMode, as in the SPIR-V specification. While ExecutionMode does exist in SPIR-V, it is something else entirely.