use strstr instead of TextFindIndex (#4764)

src/rcore.c

@@ -3696,7 +3696,7 @@ static void ScanDirectoryFiles(const char *basePath, FilePathList *files, const
                     }
                     else
                     {
-                        if (TextFindIndex(filter, DIRECTORY_FILTER_TAG) >= 0)
+                        if (strstr(filter, DIRECTORY_FILTER_TAG) != NULL)
                         {
                             strcpy(files->paths[files->count], path);
                             files->count++;
@@ -3762,7 +3762,7 @@ static void ScanDirectoryFilesRecursively(const char *basePath, FilePathList *fi
                 }
                 else
                 {
-                    if ((filter != NULL) && (TextFindIndex(filter, DIRECTORY_FILTER_TAG) >= 0))
+                    if ((filter != NULL) && (strstr(filter, DIRECTORY_FILTER_TAG) != NULL))
                     {
                         strcpy(files->paths[files->count], path);
                         files->count++;