test: move NavbarSpec, NavbarToggleSpec and NavbarBrandSpec to rtl (react-bootstrap#6196)

* move NavbarToggleSpec to rtl

* move NavbarSpec to rtl

* move NavbarBrandSpec to rtl

Author: golota60

test/NavbarBrandSpec.js

@@ -0,0 +1,24 @@
+import { render } from '@testing-library/react';
+import NavbarBrand from '../src/NavbarBrand';
+
+describe('<Navbar.Brand>', () => {
+  it('Should create NavbarBrand SPAN element', () => {
+    const { getByTestId } = render(
+      <NavbarBrand data-testid="test">Brand</NavbarBrand>,
+    );
+    const navbarBrandElem = getByTestId('test');
+    navbarBrandElem.tagName.toLowerCase().should.equal('span');
+    navbarBrandElem.classList.contains('navbar-brand').should.be.true;
+  });
+
+  it('Should create NavbarBrand A (link) element', () => {
+    const { getByTestId } = render(
+      <NavbarBrand href="/foo" data-testid="test">
+        BrandLink
+      </NavbarBrand>,
+    );
+    const navbarBrandElem = getByTestId('test');
+    navbarBrandElem.tagName.toLowerCase().should.equal('a');
+    navbarBrandElem.classList.contains('navbar-brand').should.be.true;
+  });
+});