Fix ROOT_PATH constant to match recent changes

"/" should be 0 segments, isAbsolute=true, hasTrailingSlash=false

Author: rstoyanchev

spring-web/src/main/java/org/springframework/http/server/reactive/DefaultPathSegmentContainer.java

@@ -43,7 +43,7 @@ class DefaultPathSegmentContainer implements PathSegmentContainer {
 			new DefaultPathSegmentContainer("", Collections.emptyList());
 
 	private static final PathSegmentContainer ROOT_PATH =
-			new DefaultPathSegmentContainer("/", Collections.singletonList(EMPTY_PATH_SEGMENT));
+			new DefaultPathSegmentContainer("/", Collections.emptyList());
 
 
 	private final String path;

spring-web/src/test/java/org/springframework/http/server/reactive/DefaultPathSegmentContainerTests.java

@@ -92,7 +92,7 @@ public void path() throws Exception {
 		testPath("/a/b/c", "/a/b/c", false, true, Arrays.asList("a", "b", "c"), false);
 
 		// root path
-		testPath("/", "/", false, true, Collections.singletonList(""), false);
+		testPath("/", "/", false, true, Collections.emptyList(), false);
 
 		// empty path
 		testPath("",   "", true, false, Collections.emptyList(), false);