Build: Test on Safari 18 & 17 instead of "latest-1"

JTR doesn't take into account the jump from Safari 18 to 26,
so we need to specify versions explicitly. Also, while BrowserStack
already added macOS Tahoe with Safari 26, it's not a stable release
yet, so we need to test on Safari 17 as well.

Ref jquery/jquery#5687
Ref jquery/jquery-test-runner#17

Author: mgol

.github/workflows/browserstack.yml

@@ -26,7 +26,13 @@ jobs:
         BROWSER:
           - 'IE_11'
           - 'Safari_latest'
-          - 'Safari_latest-1'
+            # JTR doesn't take into account the jump from Safari 18 to 26,
+            # so we need to specify versions explicitly. Also, while BrowserStack
+            # already added macOS Tahoe with Safari 26, it's not a stable release
+            # yet, so we need to test on Safari 17 as well.
+            # See https://github.com/jquery/jquery-test-runner/issues/17
+          - 'Safari_18'
+          - 'Safari_17'
           - 'Chrome_latest'
           - 'Chrome_latest-1'
           - 'Opera_latest'