text-anchor of first tspan anchors all tspans

[michaellisitsa]

Appears the text-anchor of the first tspan is anchoring all tspans.
e.g. Both tspans are start anchored. Middle is ignored

 <text x="10" y="30" class="small">
    <tspan x="0" dx="0" dy="0" text-anchor="start" >Start</tspan>
    <tspan x="0" dx="0" dy="15" text-anchor="middle">Middle</tspan>
  </text>

I'd previously PR'ed #2043 in v61.0 but this didn't appear to resolve the below case.

Repro:
https://replit.com/@michaellisitsa/Python-Weasyprint-tspan-v63#tspan.py

[liZe]

Thanks a lot for the report and the sample, that was really helpful.

There was quite a dirty workaround for this case, the value of the first child was always used. It should now be fixed, feedback is welcome!