Fix PerformanceObserver.supportedEntryTypes externs definition.
Fix PerformanceObserver.supportedEntryTypes externs definition.

PiperOrigin-RevId: 369276633

google/closure-compiler,monetate/closure-compiler,google/closure-compiler,ChadKillingsworth/closure-compiler,monetate/closure-compiler,nawawi/closure-compiler,ChadKillingsworth/closure-compiler,nawawi/closure-compiler,monetate/closure-compiler,nawawi/closure-compiler,ChadKillingsworth/closure-compiler,google/closure-compiler,google/closure-compiler,ChadKillingsworth/closure-compiler,monetate/closure-compiler,nawawi/closure-compiler