build: fix unneeded workaround for AC_CONFIG_LINKS old bud

build: fix unneeded workaround for AC_CONFIG_LINKS old bud

* configure.ac: The Automake NEWS entry for version 1.11 states that

    For AC_CONFIG_LINKS, if source and destination are equal, do
    not remove the file in a non-VPATH build.  Such setups work
    with Autoconf 2.62 or newer.

Since our build system requires autoconf >= 2.62 and automake >= 1.11
already, we can get rid of the workaround for that long-fixed bug.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>