chore: bump dotnet/sdk from 5.0 to 7.0 in /examples/msal-net/akvdotnet

Bumps dotnet/sdk from 5.0 to 7.0.

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

Signed-off-by: dependabot[bot] <support@github.com>

examples/msal-net/akvdotnet/Dockerfile

@@ -1,4 +1,4 @@
-FROM --platform=linux/amd64 mcr.microsoft.com/dotnet/sdk:5.0 AS builder
+FROM --platform=linux/amd64 mcr.microsoft.com/dotnet/sdk:7.0 AS builder
 WORKDIR /app
 ADD . .
 RUN dotnet build akvdotnet.csproj && dotnet publish -c release