Fix typo in Autotest color test, for dash testsuite failure.

[Ralf Wildenhues]

I ran the testsuite with my version of dash, pushing the patch below as
obvious, to fix the only failure that showed up due to a copy and paste
error from the respective Automake test.

Cheers,
Ralf

    Fix typo in Autotest color test, for dash testsuite failure.
    
    * tests/autotest.at (colored test results): Use exit not
    Exit.  Fixes test failure with dash 0.5.4.

diff --git a/tests/autotest.at b/tests/autotest.at
index 75915a8..7c0a7df 100644
--- a/tests/autotest.at
+++ b/tests/autotest.at
@@ -1571,7 +1571,7 @@ std=`printf '\033@<:@m'`
 # GNU or BSD 'grep -a' works on files, but is not portable.
 AT_CHECK([case `echo "$std" | grep .` in #'' restore font-lock
            $std) :;;
-           *) Exit 77;;
+           *) exit 77;;
          esac], [], [ignore], [],
         [echo "grep can't parse nonprinting characters" >&2])