demos: lin: fix 'async' mode of the dynamic demo #483

Job	Run time
check-run-builds	4s
Format checks for SIL Kit sources	45s
License checks for SIL Kit sources	20s
ubuntu-release-builds / clang-18 release Builds for Ubuntu	15m 37s
ubuntu-release-builds / gcc release Builds for Ubuntu	15m 42s
Undefined Behavior Sanitizer Tests / Undefined Behavior Sanitizer Tests	28m 9s
Thread Sanitizer Tests / Thread Sanitizer Tests	17m 22s
Address Sanitizer Tests / clang-asan	20m 26s
macos-release-builds / build-macos	6h 0m 14s
mingw-release-builds / msys2/mingw64 x86_64	20m 43s
ubuntu-arm-release-builds / clang-18 release Builds for Ubuntu ARM64	8m 27s
windows-release-builds / build-win-x32	19m 56s
windows-release-builds / build-win-x64	22m 29s
	8h 50m 14s

Provide feedback