fix(cli): rename the update command references to upgrade across the CLI and documentation

ts/cli.ts

@@ -266,7 +266,7 @@ export class NupstCli {
       case 'resume':
         await serviceHandler.resume();
         break;
-      case 'update':
+      case 'upgrade':
         await serviceHandler.update();
         break;
       case 'uninstall':
@@ -557,7 +557,7 @@ export class NupstCli {
     this.printCommand('config [show]', 'Display current configuration');
     this.printCommand('pause [--duration <time>]', 'Pause action monitoring');
     this.printCommand('resume', 'Resume action monitoring');
-    this.printCommand('update', 'Update NUPST from repository', theme.dim('(requires root)'));
+    this.printCommand('upgrade', 'Upgrade NUPST from repository', theme.dim('(requires root)'));
     this.printCommand('uninstall', 'Completely remove NUPST', theme.dim('(requires root)'));
     this.printCommand('help, --help, -h', 'Show this help message');
     this.printCommand('--version, -v', 'Show version information');