[glibc] malloc: Fix mallinfo deprecation declaration

[Florian Weimer]

* Adhemerval Zanella via Glibc-cvs:

> +  /* The test below covers the deprecated mallinfo function.  */
> +  DIAG_PUSH_NEEDS_COMMENT;
> +  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wdeprecated-declarations");

This should be 10 or 11, not 4.9.  The ignored diagnostics is required
for current compilers, and will always be.