Correct last query parameter type in API endpoints

[CathalMullan]

Incorrectly specified as integer in the endpoints summary.

The last query parameter provides further means for limiting the number of tags.
It is usually used in combination with the n parameter: /v2/<name>/tags/list?n=<int>&last=<tagname>

<name> is the namespace of the repository, <int> is the number of tags requested, and <tagname> is the value of the last tag.
<tagname> MUST NOT be a numerical index, but rather it MUST be a proper tag.