internal/lsp/source: document the handling of GOPRIVATE for linkTarget

Document that modules matching GOPRIVATE will not be linked.

Updates golang/vscode-go#2362

Change-Id: I7e2447bb50a2cd0d7d394f8589ccd4498f889048
Reviewed-on: https://go-review.googlesource.com/c/tools/+/419979
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
diff --git a/internal/lsp/source/api_json.go b/internal/lsp/source/api_json.go
index 94d0f12..807f496 100755
--- a/internal/lsp/source/api_json.go
+++ b/internal/lsp/source/api_json.go
@@ -116,7 +116,7 @@
 			{
 				Name:      "linkTarget",
 				Type:      "string",
-				Doc:       "linkTarget controls where documentation links go.\nIt might be one of:\n\n* `\"godoc.org\"`\n* `\"pkg.go.dev\"`\n\nIf company chooses to use its own `godoc.org`, its address can be used as well.\n",
+				Doc:       "linkTarget controls where documentation links go.\nIt might be one of:\n\n* `\"godoc.org\"`\n* `\"pkg.go.dev\"`\n\nIf company chooses to use its own `godoc.org`, its address can be used as well.\n\nModules matching the GOPRIVATE environment variable will not have\ndocumentation links in hover.\n",
 				Default:   "\"pkg.go.dev\"",
 				Hierarchy: "ui.documentation",
 			},