tests/run-tests.sh: Cleanup: Use "$srcdir" instead of "$testdir/.."
tests/run-tests.sh: Cleanup: Use "$srcdir" instead of "$testdir/.."

For clarity. In a future commit I'll have a test case that uses
"$scrdir".

stb-tester/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,wmanley/stb-tester,wmanley/stb-tester,martynjarvis/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,wmanley/stb-tester