fix: 폰트 수정 (Pretendard -> Pretendard Variable)

프리텐다드 폰트와 프리텐다드 베리어블을 헷갈렸습니다 ㅠ

Author: karpitony

src/styles/index.css

@@ -1,12 +1,7 @@
-@font-face {
-  font-family: 'Pretendard-Regular';
-  src: url('https://fastly.jsdelivr.net/gh/Project-Noonnu/noonfonts_2107@1.1/Pretendard-Regular.woff') format('woff');
-  font-weight: 400;
-  font-style: normal;
-}
+@import url("https://cdn.jsdelivr.net/gh/orioncactus/pretendard@v1.3.9/dist/web/static/pretendard-dynamic-subset.min.css");
 
 body {
-  font-family: 'Pretendard-Regular', sans-serif;
+  font-family: "Pretendard Variable", Pretendard, -apple-system, BlinkMacSystemFont, system-ui, Roboto, "Helvetica Neue", "Segoe UI", "Apple SD Gothic Neo", "Noto Sans KR", "Malgun Gothic", "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", sans-serif;
 }
 
 :root {