Bump Microsoft.AspNetCore.All from 2.1.5 to 2.1.15 in /Src/WebChatHost#1

dependabot[bot] wants to merge 1 commit intomastergabog/WebChatTestHost:masterfrom

dependabot/nuget/Src/WebChatHost/Microsoft.AspNetCore.All-2.1.15gabog/WebChatTestHost:dependabot/nuget/Src/WebChatHost/Microsoft.AspNetCore.All-2.1.15Copy head branch name to clipboard