fix: remove last_updated since git is not available on CI

docs/make_notebook_index.jl

@@ -5,18 +5,7 @@ cd(dirname(@__FILE__))
 cd("src/notebooks/") do
     contents =
         map(readdir() |> filter(!=(".gitignore")) |> filter(!=("index.html"))) do file
-            last_updated = let
-                cmdout =
-                    read(`git log $file`, String) |>
-                    IOBuffer |>
-                    eachline |>
-                    Iterators.Stateful
-                @assert popfirst!(cmdout) |> startswith("commit")
-                @assert popfirst!(cmdout) |> startswith("Author")
-                dateline = popfirst!(cmdout)
-                chopprefix(dateline, "Date:") |> strip
-            end
-            "- [`$file`]($file) (last updated: $last_updated)"
+            "- [`$file`]($file)"
         end |> (v -> join(v, '\n'))
     index_content = Markdown.parse("""
     # notebooks