fix(docs): add missing --set flag

Author: SRodi

.devcontainer/installMoreTools.sh

@@ -8,4 +8,4 @@ export LLVM_VERSION=14
 curl -sL https://apt.llvm.org/llvm.sh | sudo bash -s "$LLVM_VERSION"
 
 # Configure Git client to sign commits by default
-git config commit.gpgsign true
+git config --set commit.gpgsign true