fix(linux): remove support for upgrade

resolves #4992 as we are not able to support the upgrade command
on linux as updating oh-my-posh from within itself is impossible
to due a lock on the executable, unlike on darwin

Windows is able to update the executable after we start the installer
in the background and exit the current process

src/cli/upgrade.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"fmt"
+	"runtime"
 
 	"github.com/jandedobbeleer/oh-my-posh/src/platform"
 	"github.com/jandedobbeleer/oh-my-posh/src/upgrade"
@@ -17,6 +18,11 @@ var upgradeCmd = &cobra.Command{
 	Long:  "Upgrade when a new version is available.",
 	Args:  cobra.NoArgs,
 	Run: func(_ *cobra.Command, _ []string) {
+		if runtime.GOOS == platform.LINUX {
+			fmt.Print("\n    ⚠️ upgrade is not supported on this platform\n\n")
+			return
+		}
+
 		if force {
 			upgrade.Run()
 			return

src/upgrade/cli.go

@@ -1,3 +1,5 @@
+//go:build windows || darwin
+
 package upgrade
 
 import (

src/upgrade/cli_unix.go → src/upgrade/cli_darwin.go

@@ -1,5 +1,3 @@
-//go:build !windows
-
 package upgrade
 
 import (

src/upgrade/cli_other.go

@@ -0,0 +1,5 @@
+//go:build linux || freebsd || openbsd
+
+package upgrade
+
+func Run() {}