CMake: Remove mentions of end of life releases
    
    Sizeable portion of CMake guidelines consisted of discussing
    the difference between before and after Fedora 33.
    Fedora 33 has reached its end of life,
    so such split is not needed anymore.
    Only content referring to current situation is retained.
    
    Since out-of-source builds are now the default,
    relevant content is reordered so that out-of-source is always discussed
    before in-source, which is its opt-in alternative.
    
    Also, the link to out-of-source Fedora Change is moved so that it
    anchors to the first appearance of the term.