add 15dot7dot1 release data

Author: tglee

docs/install/visual-studio-build-numbers-and-release-dates.md

@@ -19,8 +19,7 @@ The following table lists the build numbers and release dates for Visual Studio
 
 | **Version**| **Channel** | **Release date** | **Build version** |
 | ---------------------- | ----------- | ---------------- | ----------------- |
-| 15.8.0 Preview 1.1 | Preview | May 8, 2018 |  |
-| 15.7.1 | Release | May 8, 2018 |  |
+| 15.7.1 | Release | May 8, 2018 | 15.7.27703.2000 |
 | 15.8.0 Preview 1.0 | Preview | May 7, 2018 | 15.8.27705.0 |
 | 15.7.0 | Release | May 7, 2018 | 15.7.27703.1 |
 | 15.7.0 Preview 6.0 | Preview | May 3, 2018 | 15.7.27701.1 |