Merge pull request #6932 from electron/fix-power-save-blocker-doc-bug

Fix some invalid docs

diff --cc docs/api/browser-window.md
Simple merge

diff --cc docs/api/menu-item.md
Simple merge

diff --cc docs/api/power-save-blocker.md
Simple merge

diff --cc docs/api/session.md
Simple merge

diff --cc docs/api/system-preferences.md
Simple merge

diff --cc docs/api/web-contents.md
Simple merge