[GSProcessing] Fix arg parsing error in push_gsprocessing_image (#847)

*Issue #, if available:*

*Description of changes:*

* Fix the flag letter for architecture during GSP image push

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graphstorm-processing/docker/push_gsprocessing_image.sh

@@ -58,7 +58,7 @@ parse_params() {
       EXEC_ENV="${2-}"
       shift
       ;;
-    -a | --architecture)
+    -c | --architecture)
       ARCH="${2-}"
       shift
       ;;