Bump external/glad from `2ae8255` to `8dc0d4d` #1907

Job	Run time
clang-tidy	52s
cmake-lint	18s
Codacy Security Scan	2m 57s
code-ql (cpp, gcc-14)	2m 39s
cppcheck	55s
DevSkim	28s
include-what-you-use	50s
msvc-code-analysis (RelWithDebInfo)	5m 2s
ShellCheck	17s
	14m 18s

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