style: Clean up FormText code and tests (react-bootstrap#3907)

Author: taion

src/FormText.js

@@ -32,9 +32,13 @@ const FormText = React.forwardRef(
   ({ bsPrefix, className, as: Component = 'small', muted, ...props }, ref) => {
     bsPrefix = useBootstrapPrefix(bsPrefix, 'form-text');
 
-    const classes = classNames(className, bsPrefix, muted && 'text-muted');
-
-    return <Component {...props} ref={ref} className={classes} />;
+    return (
+      <Component
+        {...props}
+        ref={ref}
+        className={classNames(className, bsPrefix, muted && 'text-muted')}
+      />
+    );
   },
 );
 

test/FormTextSpec.js

@@ -23,13 +23,8 @@ describe('<FormText>', () => {
   it('Should have "form-text" & "text-muted" class', () => {
     expect(
       mount(<FormText muted />)
-        .find('small')
-        .hasClass('form-text'),
-    ).to.equal(true);
-    expect(
-      mount(<FormText muted />)
-        .find('small')
+        .find('small.form-text')
         .hasClass('text-muted'),
-    ).to.equal(true);
+    ).to.be.true;
   });
 });