fix(vertex): append request path for custom base_url#2300

MukundaKatta wants to merge 2 commits intogoogleapis:maingoogleapis/python-genai:mainfrom

MukundaKatta:codex/python-genai-custom-base-url-pathMukundaKatta/python-genai:codex/python-genai-custom-base-url-pathCopy head branch name to clipboard