Bump github.com/mattermost/mattermost-server/v6 from 6.1.0 to 6.3.0 (#1686)

Bumps [github.com/mattermost/mattermost-server/v6](https://github.com/mattermost/mattermost-server) from 6.1.0 to 6.3.0.
- [Release notes](https://github.com/mattermost/mattermost-server/releases)
- [Changelog](https://github.com/mattermost/mattermost-server/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mattermost/mattermost-server/compare/v6.1.0...v6.3.0)

---
updated-dependencies:
- dependency-name: github.com/mattermost/mattermost-server/v6
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

vendor/golang.org/x/sys/plan9/pwd_go15_plan9.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build go1.5
 // +build go1.5
 
 package plan9

vendor/golang.org/x/sys/plan9/pwd_plan9.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !go1.5
 // +build !go1.5
 
 package plan9

vendor/golang.org/x/sys/plan9/race.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build plan9 && race
 // +build plan9,race
 
 package plan9

vendor/golang.org/x/sys/plan9/race0.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build plan9 && !race
 // +build plan9,!race
 
 package plan9

vendor/golang.org/x/sys/plan9/str.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build plan9
 // +build plan9
 
 package plan9

vendor/golang.org/x/sys/plan9/syscall.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build plan9
 // +build plan9
 
 // Package plan9 contains an interface to the low-level operating system

vendor/golang.org/x/sys/plan9/syscall_plan9.go

@@ -132,8 +132,10 @@ func Pipe(p []int) (err error) {
 	}
 	var pp [2]int32
 	err = pipe(&pp)
-	p[0] = int(pp[0])
-	p[1] = int(pp[1])
+	if err == nil {
+		p[0] = int(pp[0])
+		p[1] = int(pp[1])
+	}
 	return
 }
 

vendor/golang.org/x/sys/plan9/zsyscall_plan9_386.go

@@ -1,6 +1,7 @@
 // go run mksyscall.go -l32 -plan9 -tags plan9,386 syscall_plan9.go
 // Code generated by the command above; see README.md. DO NOT EDIT.
 
+//go:build plan9 && 386
 // +build plan9,386
 
 package plan9

vendor/golang.org/x/sys/plan9/zsyscall_plan9_amd64.go

@@ -1,6 +1,7 @@
 // go run mksyscall.go -l32 -plan9 -tags plan9,amd64 syscall_plan9.go
 // Code generated by the command above; see README.md. DO NOT EDIT.
 
+//go:build plan9 && amd64
 // +build plan9,amd64
 
 package plan9

vendor/golang.org/x/sys/plan9/zsyscall_plan9_arm.go

@@ -1,6 +1,7 @@
 // go run mksyscall.go -l32 -plan9 -tags plan9,arm syscall_plan9.go
 // Code generated by the command above; see README.md. DO NOT EDIT.
 
+//go:build plan9 && arm
 // +build plan9,arm
 
 package plan9