fix: add correct plugin name

[rwieruch]

It didn't work for me with the other plugin name.

Unfortunately, the plugin itself working for me. It shows the images in one column, but doesn't apply a grid on it. Not sure if the plugin configuration works as well, because I have used a className option but didn't see it in the DOM.

[rwieruch]

That's my configuration when using gatsby-mdx:

{
      resolve: `gatsby-mdx`,
      options: {
        extensions: ['.mdx', '.md'],
        gatsbyRemarkPlugins: [
          {
            resolve: 'gatsby-remark-grid',
            options: {
              className: 'myCustomClassName',
              gridGap: '20px',
              margin: '20px auto',
            },
          },
          {
            resolve: 'gatsby-remark-images',
            pluginOptions: {
              maxWidth: 1024,
              withWebp: true,
              linkImagesToOriginal: false,
              showCaptions: true,
            },
          },
          {
            resolve: `gatsby-remark-prismjs`,
            pluginOptions: {
              classPrefix: 'language-',
              inlineCodeMarker: null,
              aliases: {},
            },
          },
        ],
      },
    },