http2: fix FileHandle leak in respondWithFile #3195

Job	Run time
Build slim tarball	1m 35s
aarch64-linux: with shared libraries	29m 56s
aarch64-darwin: with shared libraries	57m 57s
x86_64-linux: with shared libraries	43m 9s
x86_64-darwin: with shared libraries	1h 11m 56s
	3h 24m 33s

Provide feedback