[Docs] inline details-summary title with the disclosure triangle (reduxjs#3885)

Before this change the title would drop one line under the triangle instead of
wrapping to the next line on small screens.

Former-commit-id: 86d7d14

Author: max-voronov

website/src/css/custom.css.REMOVED.git-id

@@ -1 +1 @@
-df7f2b2668b81cae16800203facde5ebd8c051b9
+90a1aa6c11de04bfbd5e8e9eba3c6c3fc8b0da82