git help config: s/insn/instruction/

"insn" appears to be an in-code abbreviation and should not appear
in manual/help pages.
Signed-off-by: NMatthias Krüger <matthias.krueger@famsik.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -525,7 +525,7 @@ core.editor::
 	`GIT_EDITOR` is not set.  See linkgit:git-var[1].
 
 sequence.editor::
-	Text editor used by `git rebase -i` for editing the rebase insn file.
+	Text editor used by `git rebase -i` for editing the rebase instruction file.
 	The value is meant to be interpreted by the shell when it is used.
 	It can be overridden by the `GIT_SEQUENCE_EDITOR` environment variable.
 	When not configured the default commit message editor is used instead.