Incorrect SPDX license identifier: "MIT."

Some files use the "MIT." license identifier.

I guess this should be "MIT", but it seems the code comes from a 3rd party project.

 It was fixed upstream in https://github.com/KhronosGroup/SPIRV-Cross/commit/f2a65545b8e8fec3ad51dedf7e25ee1cc3d1bddd on Jun 29, 2021

'MIT.' found in:

• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cfg.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cfg.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_common.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cpp.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cpp.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cross.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cross.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cross_c.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cross_c.h
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cross_containers.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cross_error_handling.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cross_parsed_ir.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cross_parsed_ir.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cross_util.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_cross_util.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_glsl.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_glsl.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_hlsl.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_hlsl.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_msl.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_msl.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_parser.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_parser.hpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_reflect.cpp
• qtshadertools/src/3rdparty/SPIRV-Cross/spirv_reflect.hpp