Dockerfile: Bump dotnet/sdk from 6.0 to 8.0.101 in /WebApi

Bumps dotnet/sdk from 6.0 to 8.0.101.

---
updated-dependencies:
- dependency-name: dotnet/sdk
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

WebApi/Dockerfile

@@ -5,7 +5,7 @@ WORKDIR /app
 EXPOSE 80
 EXPOSE 443
 
-FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
+FROM mcr.microsoft.com/dotnet/sdk:8.0.101 AS build
 WORKDIR /src
 COPY *.csproj ./
 RUN dotnet restore "WebApi.csproj"