diff-index.txt: update raw output format in examples

The two examples in the doc for 'git diff-index' were not updated when
the raw output format was changed in 81e50eabf0 ([PATCH] The diff-raw
format updates., 2005-05-21) (first example) and in b6d8f309d9 ([PATCH]
diff-raw format update take #2., 2005-05-23) and 7cb6ac1e4b (diff:
diff_aligned_abbrev: remove ellipsis after abbreviated SHA-1 value,
2017-12-03) (second example).

Update the output, inventing some characters to complete the source
hash in the second example. Also correct the destination mode in the
second example, which was wrongly '100664' since the addition of the
example in c64b9b8860 (Reference documentation for the core git
commands., 2005-05-05).

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-diff-index.txt

@@ -69,8 +69,8 @@ done an `update-index` to make that effective in the index file.
 matches my working directory. But doing a 'git diff-index' does:
 
   torvalds@ppc970:~/git> git diff-index --cached HEAD
-  -100644 blob    4161aecc6700a2eb579e842af0b7f22b98443f74        commit.c
-  +100644 blob    4161aecc6700a2eb579e842af0b7f22b98443f74        git-commit.c
+  :100644 000000 4161aecc6700a2eb579e842af0b7f22b98443f74 0000000000000000000000000000000000000000 D	commit.c
+  :000000 100644 0000000000000000000000000000000000000000 4161aecc6700a2eb579e842af0b7f22b98443f74 A	git-commit.c
 
 You can see easily that the above is a rename.
 
@@ -103,7 +103,7 @@ have not actually done a 'git update-index' on it yet - there is no
 "object" associated with the new state, and you get:
 
   torvalds@ppc970:~/v2.6/linux> git diff-index --abbrev HEAD
-  :100644 100664 7476bb... 000000...      kernel/sched.c
+  :100644 100644 7476bb5ba 000000000 M	kernel/sched.c
 
 i.e., it shows that the tree has changed, and that `kernel/sched.c` is
 not up to date and may contain new stuff. The all-zero sha1 means that to