Remove docbook that doesn't compile

ca/docs/applications/kate/index.docbook failed
fundamentals.docbook:570: parser error : Entity 'Shift' not defined

&Ctrl;&Shift;<keycap

^

fundamentals.docbook:584: parser error : Entity 'Shift' not defined

&Ctrl;&Shift;<keycap

^

fundamentals.docbook:630: parser error : Entity 'Shift' not defined

&Ctrl;&Alt;&Shift;<keycap

^

fundamentals.docbook:644: parser error : Entity 'Shift' not defined

&Ctrl;&Shift;<keycap

^

fundamentals.docbook:658: parser error : Entity 'Shift' not defined

&Ctrl;&Shift;<keycap

^

fundamentals.docbook:684: parser error : Entity 'Shift' not defined

&Shift;<keycap

^

fundamentals.docbook:700: parser error : Entity 'Shift' not defined

&Ctrl;&Shift;<keycap

^

fundamentals.docbook:989: parser error : chunk is not well balanced

^
index.docbook:146: parser error : Failure to process entity fundamentals-chapter
&fundamentals-chapter;

^

index.docbook:146: parser error : Entity 'fundamentals-chapter' not defined
&fundamentals-chapter;

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