fixed typo in prompt-bracket-checker.js which leads to js error

extensions-builtin/prompt-bracket-checker/javascript/prompt-bracket-checker.js

@@ -105,6 +105,6 @@ var shadowRootLoaded = setInterval(function() {
 
     setupBracketChecking('txt2img_prompt', 'txt2img_token_counter')
     setupBracketChecking('txt2img_neg_prompt', 'txt2img_negative_token_counter')
-    setupBracketChecking('img2img_prompt', 'imgimg_token_counter')
+    setupBracketChecking('img2img_prompt', 'img2img_token_counter')
     setupBracketChecking('img2img_neg_prompt', 'img2img_negative_token_counter')
 }, 1000);