Revert "Relax `ParenPad` checkstyle rule"

The updated formatter means that we can reinstate the rule.

This reverts commit 82fffe30.

spring-boot-parent/src/checkstyle/checkstyle.xml

@@ -147,7 +147,7 @@
 			<property name="tokens" value="BNOT, DEC, DOT, INC, LNOT, UNARY_MINUS, UNARY_PLUS, ARRAY_DECLARATOR"/>
 		</module>
 		<module name="NoWhitespaceBefore" />
-		<!-- <module name="ParenPad" /> -->
+		<module name="ParenPad" />
 		<module name="TypecastParenPad" />
 		<module name="WhitespaceAfter" />
 		<module name="WhitespaceAround" />