stop generating slides the old way after converting them to mdbook

Author: szabgab

Diff for: books.txt

@@ -3,7 +3,6 @@ ansible/ansible.json,ansible,
 ansible-intro/ansible-intro.json,ansible-intro,
 aws-lambda/aws-lambda.json,aws-lambda,
 bash/bash.json,bash,
-c/c.json,c,
 css/css.json,css,
 collab-dev/collab-dev.json,collab-dev,
 crystal/crystal.json,crystal,
@@ -15,8 +14,6 @@ google-gcp/google-gcp.json,google-gcp,
 git/git.json,git,
 git-intro/git-intro.json,git-intro,
 github-ci/github-ci.json,github-ci,
-github-pages/github-pages.json,github-pages,
-gitlab/gitlab.json,gitlab,
 golang/golang.json,golang,
 groovy/groovy.json,groovy,
 java/java.json,java,
@@ -42,15 +39,13 @@ python-mocking/python-mocking.json,python-mocking,
 python/python.json,python,
 r/r.json,r,
 raku/raku.json,raku,
-react/react.json,react,
 riot/riot.json,riot,
 ruby/ruby.json,ruby,
 scala/scala.json,scala,
 scratch/scratch.json,scratch,
 slack/slack.json,slack,
 space-fight/space-fight.json,space-fight,
 sql/sql.json,sql,
-sqlite/sqlite.json,sqlite,
 travis-ci/travis-ci.json,travis-ci,
 value/value.json,value,
 vim/vim.json,vim,
@@ -59,4 +54,3 @@ windows/windows.json,windows,
 real-world/real-world.json,real-world,
 python-pair-programming-and-tdd-workshop/python-pair-programming-and-tdd-workshop.json,python-pair-programming-and-tdd-workshop,
 what-i-learned-from-learning-rust/what-i-learned-from-learning-rust.json,what-i-learned-from-learning-rust,
-typescript/typescript.json,typescript,