fix(desktop): supersede the legacy linux packages on upgrade (#2842)

fluxer_desktop/packaging/linux/rpm-post-transaction.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+LEGACY_DIR='/opt/Fluxer Canary'
+if [ -d "$LEGACY_DIR" ]; then
+    if [ -z "$(find "$LEGACY_DIR" ! -type d -print -quit 2>/dev/null)" ]; then
+        find "$LEGACY_DIR" -depth -type d -exec rmdir {} + >/dev/null 2>&1 || true
+    fi
+fi
+
+exit 0