Make use of `highlight` tweak consistent (#2670)

* remove redundant 'highlight: false' tweaks

their inconsistent usage is super-confusing.

* Remove redundant 'value: true' on highlight tweaks

again, the inconsistency was super-confusing.

* changelog

changelogs/client_server/newsfragments/2670.clarification

@@ -0,0 +1 @@
+Minor clarifications to the "Push Notifications" module.

specification/modules/push.rst

@@ -354,10 +354,6 @@ Definition:
             {
                 "set_tweak": "sound",
                 "value": "default"
-            },
-            {
-                "set_tweak": "highlight",
-                "value": false
             }
         ]
     }
@@ -448,8 +444,7 @@ Definition:
         "actions": [
             "notify",
             {
-                "set_tweak": "highlight",
-                "value": true
+                "set_tweak": "highlight"
             }
         ]
     }
@@ -483,8 +478,7 @@ Definition:
         "actions": [
             "notify",
             {
-                "set_tweak": "highlight",
-                "value": true
+                "set_tweak": "highlight"
             }
         ]
     }
@@ -546,10 +540,6 @@ Definition:
             {
                 "set_tweak": "sound",
                 "value": "ring"
-            },
-            {
-                "set_tweak": "highlight",
-                "value": false
             }
         ]
     }
@@ -586,10 +576,6 @@ Definition:
             {
                 "set_tweak": "sound",
                 "value": "default"
-            },
-            {
-                "set_tweak": "highlight",
-                "value": false
             }
         ]
     }
@@ -622,10 +608,6 @@ Definition:
             {
                 "set_tweak": "sound",
                 "value": "default"
-            },
-            {
-                "set_tweak": "highlight",
-                "value": false
             }
         ]
     }
@@ -650,11 +632,7 @@ Definition:
             }
         ],
         "actions": [
-            "notify",
-            {
-                "set_tweak": "highlight",
-                "value": false
-            }
+            "notify"
         ]
    }
 
@@ -681,11 +659,7 @@ Definition:
             }
         ],
         "actions": [
-            "notify",
-            {
-                "set_tweak": "highlight",
-                "value": false
-            }
+            "notify"
         ]
    }