Use \thesis@blocks@preamble from fi.dtx for sci.dtx for now

See https://github.com/plk/biblatex/issues/1058 and
https://tex.stackexchange.com/a/581469/70941. The hotfix should be
reverted after BibLaTeX v3.17.

Following commit 7510875, LaTeX2e no longer identifies packages by
pathnames, but by filenames. This breaks the inheritance mechanism
of fithesis and required copying university identifier from directory
names to LaTeX package filenames. More information is available at
https://github.com/latex3/latex2e/issues/510.

This reverts commit 1f3cd34795db6fcbfdc94cd22772bc4dc24f392a.