fix a typo in NEWS.md (#2661)

* fix a typo in NEWS.md

* improve the descriptions about quo_name() and quo_text()

Author: yutannihilation

NEWS.md

@@ -18,10 +18,11 @@ To be released as 2.3.0
     constants (like `aes(x = 1)` or `aes(colour = "smoothed")`) are stored
     as is.
 
-    In this version of ggplot2, you need to describe a mapping in a string, 
-    use `quo_name()` (for shorter labels) or `quo_text()` (if you want 
-    everything). If you do need to extract the value of a variable instead use 
-    `rlang::eval_tidy()`. You may want to condition on 
+    In this version of ggplot2, if you need to describe a mapping in a string, 
+    use `quo_name()` (to generate single-line strings; longer expressions may 
+    be abbreviated) or `quo_text()` (to generate non-abbreviated strings that
+    may span multiple lines). If you do need to extract the value of a variable
+    instead use `rlang::eval_tidy()`. You may want to condition on 
     `(packageVersion("ggplot2") <= "2.2.1")` so that your code can work with
     both released and development versions of ggplot2.