Docs: add a note for no-unused-expressions (fixes #11169) (#11192)

* Docs: add a note for no-unused-expressions (fixes #11169)

* Docs: polish no-unused-expressions

docs/rules/no-unused-expressions.md

@@ -2,7 +2,7 @@
 
 An unused expression which has no effect on the state of the program indicates a logic error.
 
-For example, `n + 1;` is not a syntax error, but it might be a typing mistake where a programmer meant an assignment statement `n += 1;` instead.
+For example, `n + 1;` is not a syntax error, but it might be a typing mistake where a programmer meant an assignment statement `n += 1;` instead. Sometimes, such unused expressions may be eliminated by some build tools in production environment, which possibly breaks application logic.
 
 ## Rule Details