all: fix some comments

Change-Id: I7d5bfd4caac63820b26fc3408118c13e74e6448c
Reviewed-on: https://go-review.googlesource.com/c/sys/+/464238
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

plan9/mksyscall.go

@@ -55,7 +55,7 @@ func goBuildTags() string {
 	return strings.ReplaceAll(*tags, ",", " && ")
 }
 
-// plusBuildTags returns build tags in the +build format.
+// buildTags returns build tags in the +build format.
 func buildTags() string {
 	return *tags
 }