Revert the Steam session's D-Bus session bus

Tried on device: with a session bus the client still sat on "Switching to Desktop..." and
never reached its legacy path (no "No SteamOSManager support" line, steamos-session-select not
called), so the bus was not what it waited on. Sign-in was unaffected.

This reverts commit 40fc5463f3.

tools/linuxfs/overlay/usr/local/bin/bannerlator-session

@@ -487,23 +487,6 @@ BUSCONF
     # An update that cannot install asks for a restart (rc=42) every time; the count is capped so a
     # session can never again loop in silence, which reads as a menu opening and closing by itself.
     steam_updates=0
-    # A session bus for the client under gamescope (the desktop's labwc already runs in one). Big
-    # Picture's "Switch to Desktop" asks SteamOS Manager on it first and only then falls back to
-    # steamos-session-select (steamui.so: "No SteamOSManager support for SwitchToDesktop, using
-    # legacy path"); with no session bus at all the ask never finished and the screen sat on
-    # "Switching to Desktop..." for ever. On a bus with nothing on it the ask fails at once.
-    if [ -z "${DBUS_SESSION_BUS_ADDRESS:-}" ] && [ -z "${BL_DESKTOP:-}" ] && command -v dbus-daemon >/dev/null 2>&1; then
-      _bl_bus=/tmp/bl-session-bus-$$
-      rm -f "$_bl_bus"
-      dbus-daemon --session --address="unix:path=$_bl_bus" --nofork --nopidfile >/dev/null 2>&1 &
-      for _i in 1 2 3 4 5 6 7 8 9 10; do [ -S "$_bl_bus" ] && break; sleep 0.2; done
-      if [ -S "$_bl_bus" ]; then
-        export DBUS_SESSION_BUS_ADDRESS="unix:path=$_bl_bus"
-        echo "== steam: session bus at $_bl_bus"
-      else
-        echo "== steam: the session bus did not come up; Switch to Desktop will not work"
-      fi
-    fi
     while :; do
       rm -f "$HOME/.bl-restart-once"
       if [ -f "$steam_beta" ] && [ "$(cat "$steam_beta" 2>/dev/null)" != "$steam_channel" ]; then