[test] Mute an irText test on JS_IR instead of making it JVM-only

The test is not in any way JVM-specific, but it fails on the JS BE
because of different fq-names of stdlib symbols on JVM and JS.

The fix is in progress. Mute the test until the fix is ready.

compiler/testData/ir/irText/firProblems/timesInBuilder.kt

@@ -1,5 +1,6 @@
-// TARGET_BACKEND: JVM
 // WITH_STDLIB
+// IGNORE_BACKEND: JS_IR
+
 private fun test(x: Long) =
     countIssues {
         +(spentTime lessEq 2 * 60)