tests: remove redundant 'set -e' calls

tests: remove redundant 'set -e' calls

* tests/dist-pr109765.test: Do not set the 'errexit' shell flag,
as it is already set by 'tests/defs'.
* tests/instdir-cond.test: Likewise.
* tests/instdir-empty.test: Likewise.
* tests/lex-clean-cxx.test: Likewise.
* tests/lex-clean.test: Likewise.
* tests/lex-depend-cxx.test: Likewise.
* tests/lex-depend.test: Likewise.
* tests/lex-line.test: Likewise.
* tests/lex-nodist.test: Likewise.
* tests/lex-pr204.test: Likewise.
* tests/silent-lex.test: Likewise.
* tests/silent-yacc-headers.test: Likewise.
* tests/silent-yacc.test: Likewise.
* tests/vala-mix2.test: Likewise.
* tests/yacc-auxdir.test: Likewise.
* tests/yacc-bison-skeleton-cxx.test: Likewise.
* tests/yacc-bison-skeleton.test: Likewise.
* tests/yacc-clean-cxx.test: Likewise.
* tests/yacc-cxx.test: Likewise.
* tests/yacc-d-cxx.test: Likewise.
* tests/yacc-deleted-headers.test: Likewise.
* tests/yacc-depend.test: Likewise.
* tests/yacc-depend2.test: Likewise.
* tests/yacc-line.test: Likewise.
* tests/yacc-mix-c-cxx.test: Likewise.
* tests/yacc-weirdnames.test: Likewise.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>