Bump dotnet/aspnet in /build/docker (#4021)

Bumps dotnet/aspnet from 8.0.7-cbl-mariner2.0 to 8.0.8-cbl-mariner2.0.

---
updated-dependencies:
- dependency-name: dotnet/aspnet
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

build/docker/Dockerfile

@@ -79,7 +79,7 @@ COPY . .
 RUN dotnet publish /repo/src/Microsoft.Health.Fhir.${FHIR_VERSION}.Web/Microsoft.Health.Fhir.${FHIR_VERSION}.Web.csproj -o "/build" --no-restore -p:AssemblyVersion="${ASSEMBLY_VER}" -p:FileVersion="${ASSEMBLY_VER}" -p:Version="${ASSEMBLY_VER}" -f net8.0 -a $TARGETARCH
 
 # Implicitly uses the target platform for the runtime image.
-FROM mcr.microsoft.com/dotnet/aspnet:8.0.7-cbl-mariner2.0 AS runtime
+FROM mcr.microsoft.com/dotnet/aspnet:8.0.8-cbl-mariner2.0 AS runtime
 
 ARG FHIR_VERSION