Replace http://man7.org links with https://man7.org links.

I suspect the way http:// dies is that browsers just interpret it as
https:// anyway, but there's no reason not to just bulk fix all these at
source.

Change-Id: I38fa91728846d7c33207ef1bdadd4910eac9e941
diff --git a/libc/include/sys/statvfs.h b/libc/include/sys/statvfs.h
index 7bc5e63..2feca81 100644
--- a/libc/include/sys/statvfs.h
+++ b/libc/include/sys/statvfs.h
@@ -92,7 +92,7 @@
 #define ST_NOSYMFOLLOW 0x2000
 
 /**
- * [statvfs(3)](http://man7.org/linux/man-pages/man3/statvfs.3.html)
+ * [statvfs(3)](https://man7.org/linux/man-pages/man3/statvfs.3.html)
  * queries filesystem statistics for the given path.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
@@ -100,7 +100,7 @@
 int statvfs(const char* _Nonnull __path, struct statvfs* _Nonnull __buf);
 
 /**
- * [fstatvfs(3)](http://man7.org/linux/man-pages/man3/fstatvfs.3.html)
+ * [fstatvfs(3)](https://man7.org/linux/man-pages/man3/fstatvfs.3.html)
  * queries filesystem statistics for the given file descriptor.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.