test suite: remove useless TERM cruft in "t7005-editor.sh"

test suite: remove useless TERM cruft in "t7005-editor.sh"

In commit 15387e3 (Test suite: reset TERM to its previous value after
testing., 2007-10-26), I added a workaround to reset TERM to its previous
value before the "test_done" at the end of "t7005-editor.sh" because
otherwise "test_done" would have printed the test result with a bad TERM
env variable (this resulted in output with no color on konsole).

But since commit c2116a1 (test-lib: fix TERM to dumb for test
repeatability, 2008-03-06), colored output is printed in a subshell with
TERM reset to its original value so the earlier workaround is not needed
anymore.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>