i18n: Remove line numbers from classref PO files

It's useful context for translators but it generates very spammy diffs whenever
a line is added or removed, changing the comments for hundreds or thousands of
msgids needlessly.

We still have the file names so it's relatively easy to search in file to find
the location of the source string.

(cherry picked from commit dbfe36728ed32ee93bd200678534733c89dc3150)

doc/translations/extract.py

@@ -221,7 +221,7 @@ def _make_translation_catalog(classes):
 
 
 ## generate the catalog file
-def _generate_translation_catalog_file(unique_msgs, output):
+def _generate_translation_catalog_file(unique_msgs, output, location_line=False):
     with open(output, "w", encoding="utf8") as f:
         f.write(HEADER)
         for msg in BASE_STRINGS:
@@ -238,7 +238,10 @@ def _generate_translation_catalog_file(unique_msgs, output):
                 path = desc.desc_list.path.replace("\\", "/")
                 if path.startswith("./"):
                     path = path[2:]
-                f.write(" {}:{}".format(path, desc.line_no))
+                if location_line:  # Can be skipped as diffs on line numbers are spammy.
+                    f.write(" {}:{}".format(path, desc.line_no))
+                else:
+                    f.write(" {}".format(path))
             f.write("\n")
 
             f.write('msgid "{}"\n'.format(msg))