Bug 1721168 - Make the JS shell's default GC slice budget the same as the browser's r=sfink

This sets the budget to 5ms, as it is for the browser.

Differential Revision: https://phabricator.services.mozilla.com/D120322

js/src/shell/js.cpp

@@ -12768,7 +12768,7 @@ int main(int argc, char** argv) {
 
   bool incrementalGC = !op.getBoolOption("no-incremental-gc");
   JS_SetGCParameter(cx, JSGC_INCREMENTAL_GC_ENABLED, incrementalGC);
-  JS_SetGCParameter(cx, JSGC_SLICE_TIME_BUDGET_MS, 10);
+  JS_SetGCParameter(cx, JSGC_SLICE_TIME_BUDGET_MS, 5);
 
   JS_SetGCParameter(cx, JSGC_PER_ZONE_GC_ENABLED, true);