configure: relax flux-security version check

Problem: configure currently requires flux-security v0.14.0 or later,
but this is only required for the sdexec module, only used in system
instances and a few tests.

Now that the sdexec module and tests have runtime checks for the
flux-security version, relax the required version of flux-security
back to v0.13.0.

Note that v0.14.0 is still installed in CI and required in the debian
control file.

configure.ac

@@ -433,7 +433,7 @@ AS_IF([test x$enable_code_coverage = xyes], [
 AC_ARG_WITH([flux-security], AS_HELP_STRING([--with-flux-security],
              [Build with flux-security]))
 AS_IF([test "x$with_flux_security" = "xyes"], [
-    PKG_CHECK_MODULES([FLUX_SECURITY], [flux-security >= 0.14.0],
+    PKG_CHECK_MODULES([FLUX_SECURITY], [flux-security >= 0.13.0],
       [flux_sec_incdir=`$PKG_CONFIG --variable=includedir flux-security`])
     AS_IF([test "x$flux_sec_incdir" = x],
           [AC_MSG_ERROR([couldn't find flux-security include directory])])