Delete header_drop.jpg
Delete header_drop.jpg

remove

Former-commit-id: fb3b384d10b14078cb72b69eb39694af1e76184f [formerly bced0e86b979d1ae41a740fee523ebaccceddf36]
Former-commit-id: 86e5db23315ee3235ed5ad524951e8e72a13c833
LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io