StringBuilder can be replaced with String concatenation.

In this case the usage of `StringBuilder` has no additional benefit, since it is not inside a loop where the JVM may have problems detecting String concatenation that can be optimized. The usage of "simple" String concatenation makes the code more readable and the code will be automatically optimised by the compiler.

Original pull request #1173

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/AssignValue.java

@@ -72,7 +72,6 @@ public class AssignValue extends AbstractSegment implements Assignment {
 	@Override
 	public String toString() {
 
-		StringBuilder builder = new StringBuilder();
-		return builder.append(this.column).append(" = ").append(this.value).toString();
+		return this.column + " = " + this.value;
 	}
 }