[devcontainer] Fixing postCreateCommand path's to run properly

Author: mmmarinho

.devcontainer/postCreateCommand.sh

@@ -2,5 +2,5 @@
 set -e
 
 export PIP_BREAK_SYSTEM_PACKAGES=1
-pip install -r docs/source/requirements.txt
+pip install -r ../docs/source/requirements.txt
 pip install sphinx-autobuild