Fpm export does not include fypp preprocessed tests

[awvwgk]

The preprocessing in the fpm deployment currently assumes only the files in the source directory need to be processed using fypp:

stdlib/ci/fpm-deployment.sh

Lines 34 to 36 in 8bfcdf9

	# Preprocess stdlib sources
	find src -maxdepth 1 -iname "*.fypp" \
	| cut -f1 -d. | xargs -P "$njob" -I{} "$fypp" "{}.fypp" "$destdir/{}.f90" $fyflags

This leaves out the test_median.fypp test case.