modfile: remove duplicate words from comments

Change-Id: I47505523c97b30648f8be18fed057a6f139e6a00
GitHub-Last-Rev: c3a270cae8af3b25810959b721105c56bba9a974
GitHub-Pull-Request: golang/mod#9
Reviewed-on: https://go-review.googlesource.com/c/mod/+/424454
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: hopehook <hopehook@qq.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: hopehook <hopehook@qq.com>
Run-TryBot: Bryan Mills <bcmills@google.com>

modfile/read.go

diff --git a/modfile/read.go b/modfile/read.go
index 70947ee..a503bc2 100644
--- a/modfile/read.go
+++ b/modfile/read.go
@@ -494,7 +494,7 @@
 	in.token.endPos = in.pos
 }
 
-// peek returns the kind of the the next token returned by lex.
+// peek returns the kind of the next token returned by lex.
 func (in *input) peek() tokenKind {
 	return in.token.kind
 }