Prevent trailing comma in SCSS if() function (#18471)

Co-authored-by: fisker Cheung <lionkay@gmail.com>

changelog_unreleased/scss/18471.md

@@ -0,0 +1,15 @@
+#### Prevent trailing comma in `if()` function (#18471 by @kovsu)
+
+<!-- prettier-ignore -->
+```scss
+// Input
+$value: if(sass(false): 1; else: -1);
+
+// Prettier stable
+$value: if(
+  sass(false): 1; else: -1,
+);
+
+// Prettier main
+$value: if(sass(false): 1; else: -1);
+```