Suppress nullability constraint warning.

The variable in doubt is checked before in another method being the sole code path leading to the doBuild method.

See: #1980

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/repository/aot/JdbcCodeBlocks.java

@@ -557,6 +557,7 @@ class JdbcCodeBlocks {
 			return doBuild();
 		}
 
+		@SuppressWarnings("NullAway")
 		private CodeBlock doBuild() {
 
 			MethodReturn methodReturn = context.getMethodReturn();