This is a regression from #12864. The underscore is now too thin when the document is zoomed in.

URL: https://github.com/mozilla/pdf.js/files/2321540/issue6127.pdf
PDF.js 2.7.526: https://i.imgur.com/T4mIpct.png
PDF.js 2.7.510: https://i.imgur.com/nbwEpGT.png
Adobe Acrobat Reader DC 2020.013.20074: https://i.imgur.com/wDFBf3R.png

The screenshots were taken at 400% zoom.
if (!this.contentVisible) {
      return;
    }
    const imgData = objId.startsWith("g_")
      ? this.commonObjs.get(objId)
      : this.objs.get(objId);
    if (!imgData) {
      warn("Dependent image isn't ready yet");
      return;
    }
    const width = imgData.width;
    const height = imgData.height;
    const map = [];
    for (let i = 0, ii = positions.length; i < ii; i += 2) {
      map.push({
        transform: [scaleX, 0, 0, scaleY, positions[i], positions[i + 1]],
        x: 0,
        y: 0,
        w: width,
        h: height,
      });
    }
    this.paintInlineImageXObjectGroup(imgData, map);
  }
  paintInlineImageXObject(imgData) {