docs: copy edits for content/blog/implementing-filechute.md

[wincent]

• "explicitly syntax" → "explicit syntax"
• "on the tag which will reduce the cardinality" → "on whichever tag will reduce the cardinality"
• "may make this synchronization more efficient" → "may make this synchronization more efficient, because we can do partial or parallel synchronization"
• "simpler scheme" → "simple scheme"
• "giving only the non-revoked keys the opportunity to decrypt the data" → "giving only the non-revoked keys the opportunity to decrypt the key"
• "which is every much" → "which is very much"
• Final footnote isn't rendering properly and I don't know why