changelog: s/Fixes/Fixed/ for the header in [Unreleased]

Make sure the header matches that in the list of categories in the
changelog blurb.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ic3b47c40c00a46a2fc3e8fd30c4da94f9dc9e90a
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e04a27..ae66275 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -30,7 +30,7 @@
    - pldm_bios_table_attr_entry_string_encode()
    - pldm_bios_table_attr_entry_string_decode_def_string_length()
 
-### Fixes
+### Fixed
 
 1. pdr: Return success for pldm_pdr_find_child_container_id_range_exclude() API
 2. pdr: Rework pldm_pdr_find_container_id_range_exclude() API