git-curl-compat: remove check for curl 7.53.0

git-curl-compat: remove check for curl 7.53.0

libcurl 7.53.0 was released in February 2017, which is over seven years
ago, and no major operating system vendor is still providing security
support for it.  Debian 10 and Ubuntu 18.04, both of which are out of
mainstream security support, have supported a newer version, and RHEL 8,
which is still in support, also has a newer version.

Remove the check for this version and use this functionality
unconditionally.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>