Fix inconsistent LWLock tranche name "CommitTsSLRU"

This term was using an inconsistent casing between the code and the
documentation, using "CommitTsSLRU" in wait_event_names.txt and
"CommitTSSLRU" in the code.

Let's update the term in the code to reflect what's in the
documentation, "CommitTs" being more commonly used, so as
pg_stat_activity shows the same term as the documentation.

Oversight in 53c2a97.

Author: Alexander Lakhin
Discussion: https://postgr.es/m/f7e514cf-2446-21f1-a5d2-8c089a6e2168@gmail.com
Backpatch-through: 17

Author: michaelpq

src/backend/storage/lmgr/lwlock.c

@@ -158,7 +158,7 @@ static const char *const BuiltinTrancheNames[] = {
 	[LWTRANCHE_LAUNCHER_HASH] = "LogicalRepLauncherHash",
 	[LWTRANCHE_DSM_REGISTRY_DSA] = "DSMRegistryDSA",
 	[LWTRANCHE_DSM_REGISTRY_HASH] = "DSMRegistryHash",
-	[LWTRANCHE_COMMITTS_SLRU] = "CommitTSSLRU",
+	[LWTRANCHE_COMMITTS_SLRU] = "CommitTsSLRU",
 	[LWTRANCHE_MULTIXACTOFFSET_SLRU] = "MultixactOffsetSLRU",
 	[LWTRANCHE_MULTIXACTMEMBER_SLRU] = "MultixactMemberSLRU",
 	[LWTRANCHE_NOTIFY_SLRU] = "NotifySLRU",