Fix type in ReadFilesFromDirectory signature

PiperOrigin-RevId: 599216081

fuzztest/internal/io.cc

diff --git a/fuzztest/internal/io.cc b/fuzztest/internal/io.cc
index 9723d6d..3658908 100644
--- a/fuzztest/internal/io.cc
+++ b/fuzztest/internal/io.cc
@@ -154,7 +154,7 @@
 }
 
 std::vector<std::tuple<std::string>> ReadFilesFromDirectory(
-    std::string_view dir) {
+    absl::string_view dir) {
   std::vector<FilePathAndData> files =
       ReadFileOrDirectory({dir.data(), dir.size()});