fix(deps): download-dependencies.sh in SMStudio

chmod download-dependencies.sh to (hopefully) allow executing the
script by default after git clone. Add a branch to extract the SDK
file via Python in case the `unzip` CLI utility is not installed -
which is the case in SageMaker Studio.

download-dependencies.sh

@@ -6,5 +6,11 @@ cd ./dependencies && \
 echo "Downloading dependencies"
 curl -sS https://preview.documentation.bedrock.aws.dev/Documentation/SDK/bedrock-python-sdk.zip > sdk.zip && \
 echo "Unpacking dependencies"
-unzip sdk.zip && \
-rm sdk.zip
+# (SageMaker Studio system terminals don't have `unzip` utility installed)
+if command -v unzip &> /dev/null
+then
+    unzip sdk.zip && rm sdk.zip
+else
+    echo "'unzip' command not found: Trying to unzip via Python"
+    python -m zipfile -e sdk.zip . && rm sdk.zip
+fi