How to remove the display of the upper border of the chart grid in ngx-echarts?

I am trying to create a beautiful chart to visualize the dynamics of school students’ performance.

I am using Angular version 17.3.0, ECharts version 5.5.1, and ngx-echarts version 17.2.0.

I have this config:

{
    grid: {
      left: 20,
      right: 25,
      top: 0,
      bottom: 40,
    },
    xAxis: {
      type: 'category',
      data: [
        '9 фев',
        '16 фев',
        '23 фев',
        '1 мар',
        '8 мар',
        '15 мар',
        '22 мар',
        '29 мар',
        '5 апр',
        '12 апр',
      ],
      boundaryGap: false,
      axisLabel: {
        interval: 0,
        overflow: 'truncate',
        color: '#86909C',
        fontSize: 14,
        fontWeight: 'normal',
        margin: 10,
        formatter: (value: string) => {
          const [day, month] = value.split(' ');
          return `{a|${day}}n{b|${month}}`;
        },
        rich: {
          a: {
            fontSize: 14,
            align: 'center',
          },
          b: {
            fontSize: 14,
            align: 'center',
          },
        },
      },
      axisLine: {
        show: false,
      },
      axisTick: {
        show: false,
      },
      splitLine: {
        show: true,
        lineStyle: {
          type: 'dashed',
        },
      },
    },
    yAxis: {
      type: 'value',
      min: 1,
      max: 6,
      interval: 1,
      position: 'right',
      splitLine: {
        show: true,
        lineStyle: {
          type: 'solid',
        },
      },
      axisLabel: {
        color: '#0B1F33',
        fontSize: 16,
        fontWeight: 'bold',
        margin: 12,
        formatter: (value: number) => {
          if (value < 2 || value > 5) {
            return '';
          } else {
            return value.toString();
          }
        },
      },
    },
    series: [
      {
        name: 'Test',
        type: 'line',
        smooth: true,
        data: [null, 4, null, null, 4.57, 5, 4],
        connectNulls: true,
        emphasis: {
          focus: 'series',
        },
        itemStyle: {
          color: '#0E69D5',
          borderColor: '#ffffff',
          borderWidth: 1,
        },
        lineStyle: {
          color: '#185AC5',
        },
        symbol: 'circle',
        symbolSize: 7,
        markLine: {
          symbol: 'none',
          tooltip: { show: false },
          label: { show: false },
          data: [
            {
              xAxis: 6,
              lineStyle: {
                color: '#0E69D5',
                width: 1,
                type: 'solid',
              },
              emphasis: {
                disabled: true,
              },
            },
          ],
        },
        areaStyle: {
          color: {
            type: 'linear',
            x: 0,
            y: 0,
            x2: 0,
            y2: 1,
            colorStops: [
              { offset: 0, color: 'rgba(192, 216, 253, 0.80)' },
              { offset: 1, color: 'rgba(237, 247, 255, 0.08)' },
            ],
          },
        },
      },
    ],
  }

This is how it looks:

How can I hide the line I marked in red? Or is this impossible to do with ECharts? If it’s impossible, could you please recommend other libraries?