git/instructor.md: git -> Git where appropriate

diff --git a/git b/git
index ad0c8b89d9f134462df11bd80a0e2a8a61a0a08d..0ea0528e9acb696852d48396987d4f826719044f 160000 (submodule)
--- a/git
+++ b/git
@@ -1 +1 @@
-Subproject commit ad0c8b89d9f134462df11bd80a0e2a8a61a0a08d
+Subproject commit 0ea0528e9acb696852d48396987d4f826719044f