DOC: fixes empty boxes + too wide:
- excel: code snippets too wide
- visualisation: for some reason now empty boxes when ipython code blocks with plt.figure were suppressed, but not when removing the semicolon
DOC: improve docstring of pd.melt
Merge pull request #6746 from jorisvandenbossche/doc-fixes

Doc fixes
PRF: Optimize axis1 for C order