QVarLengthArray: fix insert() type/alias mismatch between decl and impl

The declaration of insert(it, n, t) used qsizetype for n, while the definition used size_type. That works by chance, because the size_type typedef comes only after the insert(it, n, t) declaration. It was detected when size_type became a typedef in a base class of QVarLengthArray in my local branch.

Just use the same type name in the implementation as in the declaration.

In 5.15, the same issue exists (with s/qsizetype/int/).

Pick-to: 6.2 5.15 Change-Id: I64235eeaeaed3d43f4c070ca536474fae94c1b5d Reviewed-by: Mårten Nordheim marten.nordheim@qt.io (cherry picked from commit fd1a4249)