misc: bump Smithy version (#1436)

Author: lauzadis

.changes/6604e856-ab5c-44ab-968b-3a2c57e7a35b.json

@@ -0,0 +1,5 @@
+{
+    "id": "6604e856-ab5c-44ab-968b-3a2c57e7a35b",
+    "type": "misc",
+    "description": "Upgrade to Smithy 1.51.0"
+}

gradle/libs.versions.toml

@@ -9,11 +9,11 @@ coroutines-version = "1.9.0"
 atomicfu-version = "0.24.0"
 
 # smithy-kotlin codegen and runtime are versioned separately
-smithy-kotlin-runtime-version = "1.3.14"
-smithy-kotlin-codegen-version = "0.33.14"
+smithy-kotlin-runtime-version = "1.3.15"
+smithy-kotlin-codegen-version = "0.33.15"
 
 # codegen
-smithy-version = "1.50.0"
+smithy-version = "1.51.0"
 
 # testing
 junit-version = "5.10.1"