feat: remove Korean page

[DennisPitallano]

• issue Remove Korean language from DigiByte .org #158
  This pull request removes Korean language support from the website's language menus and sitemap, making Korean (ko) no longer available as a selectable or discoverable option. It also makes a minor update to the language routing logic.

Removal of Korean language support:

• Removed Korean (ko) from the desktop language menu in langmenu/desktop.html.
• Removed Korean (ko) from the mobile language menu in langmenu/mobile.html.
• Removed all <xhtml:link rel="alternate" hreflang="ko" ... /> entries from sitemap.xml, so Korean is no longer listed as an alternate language for search engines. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22]

Minor language routing update:

• Updated the language routing logic in js/languagerouter.js by removing ko from the list of supported languages for redirection.

[gto90]

utACK

[ycagel]

cACK. Thanks for all the efforts @DennisPitallano!