Since the One UI Watch 4.5 beta program for the Galaxy Watch4 series was closed by Samsung on its community forums, the Korean conglomerate will not release any new beta builds for the Watch4 series. The beta program began a few months ago. Although Samsung hasn't officially announced it, some Galaxy Watch4 owners have already begun receiving the stable One UI Watch 4.5 upgrade.
The 95MB download includes firmware versions R870XXU1GVH2/R870OXM1GVH2. If you haven't received the update notification yet, you may check for it manually by going to Galaxy Wearable > Galaxy Watch4 > Watch4 settings > Watch software update.