pdr: Stabilise pldm_pdr_find_last_in_range() API

Use of pldm_pdr_find_last_in_range() API is demonstarted here:
https://gerrit.openbmc.org/c/openbmc/pldm/+/63125

Change-Id: Idf51abc591fd2e2ab31f3b7e1d2957d1345702e7
Signed-off-by: Pavithra Barithaya <pavithra.b@ibm.com>
diff --git a/src/pdr.c b/src/pdr.c
index 9a9c11a..9cebd27 100644
--- a/src/pdr.c
+++ b/src/pdr.c
@@ -1095,7 +1095,7 @@
 	}
 }
 
-LIBPLDM_ABI_TESTING
+LIBPLDM_ABI_STABLE
 pldm_pdr_record *pldm_pdr_find_last_in_range(const pldm_pdr *repo,
 					     uint32_t first, uint32_t last)
 {