book: update sl

Updated via the `update-book.yml` GitHub workflow.

Author: dscho

external/book/content/book/sl/v2/_index.html

@@ -8,9 +8,9 @@
   language_code: sl
   front_page: true
   repository_url: https://github.com/progit/progit2-sl
-  sha: 03aedc2133e5a269223bde7159757e2c3a952b72
-  ebook_pdf: https://github.com/progit/progit2-sl/releases/download/2.1.90/progit.pdf
-  ebook_epub: https://github.com/progit/progit2-sl/releases/download/2.1.90/progit.epub
+  sha: a0a22228fa14c053ed03a3d93653385c28c77f78
+  ebook_pdf: https://github.com/progit/progit2-sl/releases/download/2.1.91/progit.pdf
+  ebook_epub: https://github.com/progit/progit2-sl/releases/download/2.1.91/progit.epub
 page_title: Git - Book
 url: "/book/sl/v2.html"
 aliases:

external/book/sync/book-sl.sha

@@ -1 +1 @@
-03aedc2133e5a269223bde7159757e2c3a952b72
+a0a22228fa14c053ed03a3d93653385c28c77f78