package.json: rename vulncheck command

From "Run Vulncheck (Experiment)" to "Run Vulncheck (Preview)"

Change-Id: I1ea060e67c8611cdd76d9e83e23840cf8bad2e1c
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/429237
Reviewed-by: Jamal Carvalho <jamal@golang.org>
Reviewed-by: Suzy Mueller <suzmue@golang.org>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>

Author: hyangah

docs/commands.md

@@ -263,6 +263,6 @@ Edit the Go Env for the active workspace.
 
 Reset the Go Env for the active workspace.
 
-### `Go: Run Vulncheck (Experimental)`
+### `Go: Run Vulncheck (Preview)`
 
-Run go vulncheck.
+Run vulnerability check. See https://pkg.go.dev/golang.org/x/vuln/cmd/govulncheck for more details about the analysis.

package.json

@@ -523,8 +523,8 @@
       },
       {
         "command": "go.vulncheck.run",
-        "title": "Go: Run Vulncheck (Experimental)",
-        "description": "Run go vulncheck.",
+        "title": "Go: Run Vulncheck (Preview)",
+        "description": "Run vulnerability check. See https://pkg.go.dev/golang.org/x/vuln/cmd/govulncheck for more details about the analysis.",
         "enablement": "go.goplsIsRunning"
       }
     ],