Fix missing namespace qualifier in TupleVector.

[eugeneko]

Trivial compilation fix for tuple vector used with STD iterator tags.

[grojo-ea]

Hello @eugeneko,

Thanks for the PR, it looks good to me but it looks like we don't have a CLA for you on file yet. Could you please fill out this form before we merge this?

Thanks again.

[eugeneko]

I am sure I signed up this thing before my first PR to EASTL. Did it again just in case.

[grojo-ea]

Thanks for filling out that form, we have on file now so we're good to merge this change.