Fix unstable broken-ref test (#1714)

In this test, OCamlformat calls git diff then tries to hide the
temporary file names in the output. This didn't work on my system, where
temporary files are created into `/run/user/...` instead of `/tmp`.

Author: Julow

lib/Translation_unit.ml

@@ -55,14 +55,9 @@ module Error = struct
     let n = Filename.temp_file input_name (Printf.sprintf ".next%s" ext) in
     Out_channel.write_all p ~data:prev ;
     Out_channel.write_all n ~data:next ;
-    let anonymize =
-      "sed 's/a\\/tmp\\/[^ ]*/before/g' | sed 's/b\\/tmp\\/[^ ]*/after/g' | \
-       sed '/index .*/d'"
-    in
     ignore
       (Caml.Sys.command
-         (Printf.sprintf "git diff --no-index -u %S %S | %s 1>&2" p n
-            anonymize ) ) ;
+         (Printf.sprintf "git diff --no-index -u %S %S | sed '1,4d' 1>&2" p n) ) ;
     Caml.Sys.remove p ;
     Caml.Sys.remove n
 

test/failing/tests/unstable_docstrings.mli.broken-ref

@@ -3,9 +3,6 @@ ocamlformat: Cannot process "tests/unstable_docstrings.mli".
   BUG: doc comments changed.
 File "_none_", line 0, characters -1--1::
 Error: Formatting of doc-comment is unstable (e.g. parses as a list or not depending on the margin):
-diff --git before after
---- before
-+++ after
 @@ -1,6 +1,7 @@
   Blablabla. Otherwise, the given protocol can not be:
 -    {ul