Gource captions: Fix capitalization of "Metamath"
Gource captions: Fix capitalization of "Metamath"

"Metamath" wasn't capitalized in two Gource caption lines;
fix that.

Signed-off-by: David A. Wheeler <9ae72d22d8b894b865a7a496af4fab6320e6abb2@dwheeler.com>

metamath/set.mm,metamath/set.mm,metamath/set.mm