dockerimg: remove buildx dependencies from Dockerfile

Main changes:
1. Removed --mount=type=cache for apt-get operations and added cleanup steps
2. Removed --mount=type=cache for Go tools installation

Co-Authored-By: sketch <hello@sketch.dev>
diff --git a/dockerimg/testdata/testcreatedockerfile_basic_repo_with_readme.dockerfile b/dockerimg/testdata/testcreatedockerfile_basic_repo_with_readme.dockerfile
index 49bea1c..b23552a 100644
--- a/dockerimg/testdata/testcreatedockerfile_basic_repo_with_readme.dockerfile
+++ b/dockerimg/testdata/testcreatedockerfile_basic_repo_with_readme.dockerfile
@@ -1,4 +1,4 @@
-FROM ghcr.io/boldsoftware/sketch:86ef7a672f85139e73f38d4cdf78d95f
+FROM ghcr.io/boldsoftware/sketch:3a03b430af3cabf3415d263b7803b311
 
 ARG GIT_USER_EMAIL
 ARG GIT_USER_NAME
@@ -6,12 +6,12 @@
 RUN git config --global user.email "$GIT_USER_EMAIL" && \
     git config --global user.name "$GIT_USER_NAME"
 
-LABEL sketch_context="2f264f73c8a474c0901bf67b0b1ae2ffe24afc4aceabc27435efbd70ed4c36ab"
+LABEL sketch_context="1904f4ae13566afc998b89a591dd37bac3bbe5ee0811b3c8c5d017baa0b7a924"
 COPY . /app
 
 WORKDIR /app
 RUN if [ -f go.mod ]; then go mod download; fi
 
-# No additional setup needed for this simple Go test project
+RUN echo "Setting up test project environment" || true
 
 CMD ["/bin/sketch"]