xbps-src: remove WIP repo delta support.

- it never worked correctly
- it's WIP and looks like it will be stalled forever
- won't be necessary anymore with xbps-0.42

xbps-src

@@ -116,8 +116,6 @@ Options:
 -C  Do not remove build directory, automatic dependencies and
     package destdir after successful install.
 
--D  Generate repository binary diffs (deltas) via xdelta3.
-
 -f  Force building and registering binary packages into the local repository,
     even if same version is already registered.
 
@@ -314,11 +312,10 @@ readonly XBPS_MACHINE=$(uname -m)
 #
 XBPS_OPTIONS=
 
-while getopts "a:CDfgGhH:Ij:Lm:No:r:V" opt; do
+while getopts "a:CfgGhH:Ij:Lm:No:r:V" opt; do
     case $opt in
         a) readonly XBPS_CROSS_BUILD="$OPTARG"; XBPS_OPTIONS+="-a $OPTARG ";;
         C) readonly XBPS_KEEP_ALL=1; XBPS_OPTIONS+="-C ";;
-        D) readonly XBPS_REPO_DELTAS=1; XBPS_OPTIONS+=" -D";;
         f) readonly XBPS_BUILD_FORCEMODE=1; XBPS_OPTIONS+="-f ";;
         G) readonly XBPS_USE_GIT_REVS=1; XBPS_OPTIONS+="-G ";;
         g) readonly XBPS_DEBUG_PKGS=1; XBPS_OPTIONS+="-g ";;