Drop support for Safari 15

Safari 15:

* Lacks structuredClone, which is starting to become useful
* Has stack trace quirks that are not well understood, not properly handled
  by Jasmine, and can cause problems in Jasmine's own tests
* Is not widely used
* Does not run on any OS that still receives security updates

README.md

@@ -30,7 +30,7 @@ Microsoft Edge) as well as Node.
 | Environment       | Supported versions               |
 |-------------------|----------------------------------|
 | Node              | 18.20.5+*, 20, 22, 24            |
-| Safari            | 15*, 16*, 17*                    |
+| Safari            | 16*, 17*                         |
 | Chrome            | Evergreen                        |
 | Firefox           | Evergreen, 102*, 115*, 128*, 140 |
 | Edge              | Evergreen                        |

package.json

@@ -52,7 +52,7 @@
     "sass": "^1.58.3"
   },
   "browserslist": [
-    "Safari >= 15",
+    "Safari >= 16",
     "Firefox >= 102",
     "last 2 Chrome versions",
     "last 2 Edge versions"

scripts/run-all-browsers

@@ -39,14 +39,8 @@ else
 fi
 run_browser firefox 102
 
-
 run_browser safari 17
-if [ "$1" = "--not-actually-all" ]; then
+run_browser safari 16
-  echo "SKIPPED: safari 16" >> "$passfile"
-else
-  run_browser safari 16
-fi
-run_browser safari 15
 
 run_browser MicrosoftEdge latest