configure: remove hack to add quotes to $DEVENV again

This was added because CPPUNITTRACE='"$(DEVENV)" /debugexe' is less
convenient to write than CPPUNITTRACE='$(DEVENV) /debugexe'.

However DavidO points out that CPPUNITTRACE=TRUE is even more
convenient and sort of optimal already, and it turns out it's broken by
the extra quotes, so remove the hack.

Change-Id: Ic5d94f9a0774cd41821b68728404c205552d674e
Reviewed-on: https://gerrit.libreoffice.org/35589Reviewed-by: David Ostrovsky <david@ostrovsky.org>
Tested-by: Jenkins <ci@libreoffice.org>

configure.ac

@@ -3456,8 +3456,6 @@ if test "$_os" = "WINNT"; then
     if test ! -e "$DEVENV"; then
         AC_MSG_ERROR([No devenv.exe found, Visual Studio installation broken?])
     fi
-    # add quotes around it, this is an ugly hack for convenience
-    DEVENV=\"${DEVENV}\"
 
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     dnl  Check for the corresponding mspdb*.dll