Fix tests according to postcss-selector-not latest fix

Author: MoOx

src/__tests__/fixtures/cases/example.actual.css

@@ -75,7 +75,7 @@ a:after {
 p:first-child, p.specific {
   color: red;
 }
-p:not(:first-child), p:not(.specific) {
+p:not(:first-child):not(.specific) {
   background: blue;
 }
 

src/__tests__/fixtures/cases/example.expected.css

@@ -75,7 +75,7 @@ a:after {
 p:first-child, p.specific {
   color: red;
 }
-p:not(:first-child), p:not(.specific) {
+p:not(:first-child):not(.specific) {
   background: blue;
 }
 

src/__tests__/fixtures/features/pseudo-class-not.expected.css

@@ -1,3 +1,3 @@
-p:not(:first-child), p:not(.specific) {
+p:not(:first-child):not(.specific) {
   background: blue;
 }