Remove @TestApi and @Readable for NFC_PAYMENT_DEFAULT_COMPONENT

Remove @Readable for security vulnerability.
Remove @TestApi since there's no exceptions in ReadSettingsFieldsTest

Bug: 191519696
Bug: 174151290
Test: atest CtsNfcTestCases
Test: atest android.appsecurity.cts.ReadableSettingsFieldsTest
Test: atest CtsQuickAccessWalletTestCases
Test: make RunSettingsRoboTests -j
Test: atest QuickAccessWalletTileTest
Merged-In: I13c038753d3acf3f3b651af3cd22ff55cd464cb1
Change-Id: I13c038753d3acf3f3b651af3cd22ff55cd464cb1