feat(Polynomial.js): Fixed bad code

Maths/Polynomial.js

@@ -32,11 +32,9 @@ class Polynomial {
           return `(${coefficient}x^${exponent})`
         }
       })
-      .filter((x) => {
+      .filter((x) =>
-        if (x !== '0') {
+        x !== '0'
-          return x
+      )
-        }
-      })
       .reverse()
       .join(' + ')
   }