fix: return previous color state from setColorsEnabled (#3002)

Author: cuiweixie

NOTICE

@@ -62,6 +62,7 @@ under the licensing terms detailed in LICENSE:
 * Kam Chehresa <kaz.che@gmail.com>
 * Mopsgamer <79159094+Mopsgamer@users.noreply.github.com>
 * EDM115 <github@edm115.dev>
+* Weixie Cui <cuiweixie@gmail.com>
 
 Portions of this software are derived from third-party works licensed under
 the following terms:

src/util/terminal.ts

@@ -32,7 +32,7 @@ export function isColorsEnabled(): bool {
 
 /** Sets whether terminal colors are enabled or not. */
 export function setColorsEnabled(isEnabled: bool): bool {
-  let wasEnabled = isEnabled;
+  let wasEnabled = colorsEnabled;
   colorsEnabled = isEnabled;
   return wasEnabled;
 }