docs: update bad undo-add links (#1823)

* docs: update bad undo-add links
per https://github.com/iterative/dvc.org/runs/1179565776

* Update content/docs/command-reference/remove.md

* Update content/docs/command-reference/unprotect.md

* Update content/docs/user-guide/large-dataset-optimization.md

* Update content/docs/user-guide/large-dataset-optimization.md

content/docs/command-reference/remove.md

@@ -34,8 +34,8 @@ Note that in the case of `.dvc` file `targets`, the tracked files or directories
 `dvc gc`). However, remember to run `dvc push` to save the files you actually
 want to use or share in the future.
 
-Refer to [Updating Tracked Files](/doc/user-guide/updating-tracked-files) to see
-how it can be used to replace or modify files that are tracked by DVC.
+Refer to [Updating Tracked Files](/doc/user-guide/how-to/update-tracked-files)
+to see how it can be used to replace or modify files that are tracked by DVC.
 
 ## Options
 

content/docs/command-reference/unprotect.md

@@ -26,8 +26,8 @@ modifying file links.)
 Running `dvc unprotect` guarantees that the target files or directories
 (`targets`) in the workspace are physically "unlinked" from the cache and can be
 safely updated. Read the
-[Update a Tracked File](/doc/user-guide/updating-tracked-files) guide to learn
-more on this process.
+[Update a Tracked File](/doc/user-guide/how-to/update-tracked-files) guide to
+learn more on this process.
 
 `dvc unprotect` can be an expensive operation (involves copying data). Check
 first whether your task matches one of the cases that are considered safe:

content/docs/user-guide/large-dataset-optimization.md

@@ -100,8 +100,8 @@ efficiency:
 
 > DVC avoids `symlink` and `hardlink` types by default to protect user from
 > accidental cache corruption. Refer to the
-> [Update a Tracked File](/doc/user-guide/updating-tracked-files) guide to learn
-> more.
+> [Update a Tracked File](/doc/user-guide/how-to/update-tracked-files) guide to
+> learn more.
 
 ## Configuring DVC cache file link type
 
@@ -117,9 +117,9 @@ $ dvc config cache.type hardlink,symlink
 > Refer to `dvc config cache` for more details.
 
 Note that with this `cache.type`, your workspace files will be in read-only mode
-in order to protect the cache from corruption. Please refer to the
-[Update a Tracked File](/doc/user-guide/updating-tracked-files) on how to manage
-tracked files under these cache configurations.
+in order to protect the cache from corruption. Please refer to
+[Update a Tracked File](/doc/user-guide/how-to/update-tracked-files) on how to
+manage tracked files under these cache configurations.
 
 To make sure that the data files in the workspace are consistent with the
 <abbr>project</abbr>'s `cache.type` config value, you may use