[web] Removed pandoc leftovers.

web/assets/scss/main.scss

web/assets/scss/pandoc-highlighting.scss

web/content/.markdownlintignore

...docs/benchmarks/heat-transport-bhe/3D_BHE_GW_advection.md

...content/docs/benchmarks/hydro-component/theis/HC_Theis.md

...all-deformations/mechanics-linear-element_deactivation.md

web/content/docs/devguide/advanced/docker.md

web/content/docs/devguide/advanced/gitlab-migration.md

web/content/docs/devguide/advanced/redistributable-builds.md

web/content/docs/devguide/advanced/singularity.md

web/content/docs/devguide/advanced/third-party-libraries.md

web/content/docs/devguide/advanced/working-on-eve.md

web/content/docs/devguide/advanced/wsl.md

.../devguide/development-workflows/continuous-integration.md

...tent/docs/devguide/getting-started/build-configuration.md

web/content/docs/devguide/getting-started/prerequisites.md

web/content/docs/devguide/troubleshooting/build.md

web/content/docs/devguide/troubleshooting/cmake.md

web/content/docs/userguide/basics/envinf1.md

web/content/imprint.md