docs: add missing leading slashes in help patterns (#5869)

docs: add missing leading slashes in help patterns, fixes #5857

src/borg/archiver.py

@@ -2367,8 +2367,8 @@ class Archiver:
             /home/*/junk
             *.tmp
             fm:aa:something/*
-            re:^home/[^/]\\.tmp/
-            sh:home/*/.thumbnails
+            re:^/home/[^/]+\\.tmp/
+            sh:/home/*/.thumbnails
             # Example with spaces, no need to escape as it is processed by borg
             some file with spaces.txt
             EOF