Remove jujutsu directory from search tools. (rust-lang#15695)

This prevents ripgrep from searching the directory by default.

changelog: none

Author: samueltardieu

.gitignore

@@ -48,3 +48,6 @@ helper.txt
 
 # mdbook generated output
 /book/book
+
+# Remove jujutsu directory from search tools
+.jj