doc: avoid using the gender of other people

Using gendered pronouns for an anonymous person applies a gender where
none is known and further excludes readers who do not use gendered
pronouns. Avoid such examples in the documentation by using "they" or
passive voice to avoid the need for a pronoun.

Inspired-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/user-manual.txt b/Documentation/user-manual.txt
index fd480b8..2983e3b 100644
--- a/Documentation/user-manual.txt
+++ b/Documentation/user-manual.txt
@@ -2789,7 +2789,7 @@
 
 In some cases it is possible that the new head will *not* actually be
 a descendant of the old head.  For example, the developer may have
-realized she made a serious mistake, and decided to backtrack,
+realized a serious mistake was made and decided to backtrack,
 resulting in a situation like:
 
 ................................................