Migrate from android::String isEmpty to empty

This empty method is different from the old one - it aligns with
std::string definition.

Bug: 295394788
Test: make checkbuild
Change-Id: Id6baed8cde01a75a8839ad6b4475a31ba1f49c8a
diff --git a/libutils/String8_fuzz.cpp b/libutils/String8_fuzz.cpp
index e5dcd31..09dcacd 100644
--- a/libutils/String8_fuzz.cpp
+++ b/libutils/String8_fuzz.cpp
@@ -34,7 +34,7 @@
                     str1->bytes();
                 },
                 [](FuzzedDataProvider*, android::String8* str1, android::String8*) -> void {
-                    str1->isEmpty();
+                    str1->empty();
                 },
                 [](FuzzedDataProvider*, android::String8* str1, android::String8*) -> void {
                     str1->length();