t/lib-*.sh: drop executable bit

There's no need for shell libraries to have the executable bit. They're
meant to be sourced, and running them stand-alone is pointless. Let's
reduce any possible confusion by making it more clear they're not meant
to be run this way.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/lib-credential.sh b/t/lib-credential.sh
old mode 100755 (executable)
new mode 100644 (file)

diff --git a/t/lib-gpg.sh b/t/lib-gpg.sh
old mode 100755 (executable)
new mode 100644 (file)

diff --git a/t/lib-log-graph.sh b/t/lib-log-graph.sh
old mode 100755 (executable)
new mode 100644 (file)

diff --git a/t/lib-submodule-update.sh b/t/lib-submodule-update.sh
old mode 100755 (executable)
new mode 100644 (file)