tree-wide: Remove O_CLOEXEC from fdopen

fdopen doesn't accept "e", it's ignored. Let's not mislead people into
believing that it actually sets O_CLOEXEC.

From `man 3 fdopen`:

> e (since glibc 2.7):
> Open the file with the O_CLOEXEC flag. See open(2) for more information. This flag is ignored for fdopen()

As mentioned by @jlebon in #11131.

src/basic/fileio.c

@@ -156,7 +156,7 @@ int write_string_file_ts(
                         goto fail;
                 }
 
-                f = fdopen(fd, "we");
+                f = fdopen(fd, "w");
                 if (!f) {
                         r = -errno;
                         safe_close(fd);

src/basic/tmpfile-util.c

@@ -36,7 +36,7 @@ int fopen_temporary(const char *path, FILE **_f, char **_temp_path) {
                 return -errno;
         }
 
-        f = fdopen(fd, "we");
+        f = fdopen(fd, "w");
         if (!f) {
                 unlink_noerrno(t);
                 free(t);