Checkmk Werk 13334: Drop support for Internet Explorer 11 (IE11)

ID: 13334 Title: Drop support for Internet Explorer 11 (IE11) Component: Multisite Level: 2 Class: New feature Version: 2.1.0i1 The support for IE11 is dropped beginning with version 2.1 of Checkmk. Since some of our dependencies already dropped the support and we don't want to ship old/outdated versions we are dropping support for IE11 as well, prior to the official end of life at 2022-06-15.