Fixed the author name

In the section 2.3, if one wants to see the changes made by the author
Junio Hamano, the author name cannot be gitster. Fixed the same.

Author: Snehal Shekatkar

book/02-git-basics/sections/viewing-history.asc

@@ -284,7 +284,7 @@ For example, if you want to see which commits modifying test files in the Git so
 
 [source,console]
 ----
-$ git log --pretty="%h - %s" --author=gitster --since="2008-10-01" \
+$ git log --pretty="%h - %s" --author=Junio Hamano --since="2008-10-01" \
    --before="2008-11-01" --no-merges -- t/
 5610e3b - Fix testcase failure when extended attributes are in use
 acd3b9e - Enhance hold_lock_file_for_{update,append}() API