Bump dotnet/sdk in /samples/managed-identity

Bumps dotnet/sdk from 7.0-cbl-mariner2.0 to 8.0.101-cbl-mariner2.0.

---
updated-dependencies:
- dependency-name: dotnet/sdk
  dependency-type: direct:production
...

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

samples/managed-identity/Dockerfile

@@ -5,7 +5,7 @@ ARG TARGETARCH
 WORKDIR /app
 EXPOSE 80
 
-FROM mcr.microsoft.com/dotnet/sdk:7.0-cbl-mariner2.0@sha256:9e054d0663d07e09127d114f753c1068d0bf681eab188352d06f111ce68f050f AS build
+FROM mcr.microsoft.com/dotnet/sdk:8.0.101-cbl-mariner2.0@sha256:e14034d5ba09b02204d56e809343586475433fd021938488088ccc5cae9d3cd2 AS build
 ARG TARGETARCH
 WORKDIR /src
 COPY "mi-webapp.csproj" .