Disable gcrypt in RHEL

The libgcrypt functionality is used only by the AFP backend which is not
built on RHEL, but it is still required from meson.build, regardless of
the -Dafp=false option. Let's add the -Dgcrypt=false option to fix this.

gvfs.spec

@@ -235,6 +235,7 @@ the functionality of the installed gvfs package.
 %if 0%{?rhel} >= 9
        -Darchive=false \
        -Dafp=false \
+       -Dgcrypt=false \
 %endif
         %{nil}
 %meson_build