examples-from-user-filed-issues.md: clarify multiple corruption handling

Some users may be tempted to only replace one out of several corrupt
objects and then try to see how filter-repo handles it.  The problem is
that having any corrupt object is likely to cause one of fast-export,
filter-repo, or fast-import to fail.  Make it clear that all corrupt
objects need to be replaced before running filter-repo.  (There are some
types of corruption that none of the systems will fail on, and which you
can thus replace one at a time, but we don't want users relying on that
and then coming back to us and asking why it doesn't work.)

Signed-off-by: Elijah Newren <[email protected]>

Author: newren

Documentation/examples-from-user-filed-issues.md

@@ -300,9 +300,10 @@ $ rm tmp
 $ git filter-repo --proceed
 ```
 
-Note that if you have multiple corrupt objects, you only need to run
-filter-repo once; that is, so long as you create all the replacements
-before you run filter-repo.
+Note that if you have multiple corrupt objects, you need to create
+replacements for all of them, and then run filter-repo.  Leaving any
+corrupt object without a replacement is likely to cause the filter-repo run
+to fail.
 
 ### Handling repository corruption -- tree objects