Recolor crosses in medical emoji

[e2-71828]

In most jurisdictions, use of the red cross symbol is extremely restricted by the Geneva Convention, which makes the color version of several OpenMoji extension glyphs unsuitable for use:

• https://openmoji.org/library/emoji-E300/
• https://openmoji.org/library/emoji-E301/
• https://openmoji.org/library/emoji-E302/
• https://openmoji.org/library/emoji-E303/
• https://openmoji.org/library/emoji-E307/
• https://openmoji.org/library/emoji-E309/
• https://openmoji.org/library/emoji-E30A/
• https://openmoji.org/library/emoji-E30B/
• https://openmoji.org/library/emoji-E140/

The simplest fix would be to recolor these to be either blue or green.

For E309 and E140 specifically, a white cross on a green square makes sense as that's the ISO standard first aid symbol.

[e2-71828]

Related: #417