Bump compileSdkVersion for bramble-android.

bramble-android/build.gradle

@@ -3,7 +3,7 @@ apply plugin: 'witness'
 apply from: 'witness.gradle'
 
 android {
-	compileSdkVersion 27
+	compileSdkVersion 28
 	buildToolsVersion '28.0.2'
 
 	defaultConfig {

bramble-android/witness.gradle

 dependencyVerification {
     verify = [
-        'Android:Sdk:platforms:android.jar:c94be7c1b823cd9672636f92d3c995e85cecb3674b2cbd4e8614db731367dc7f',
         'cglib:cglib:3.2.0:cglib-3.2.0.jar:adb13bab79712ad6bdf1bd59f2a3918018a8016e722e8a357065afb9e6690861',
         'com.android.tools.analytics-library:protos:26.2.0:protos-26.2.0.jar:306784ac579be37f64f110204ea3fad8568e09e10817bb574bac0fc71b6402c5',
         'com.android.tools.analytics-library:shared:26.2.0:shared-26.2.0.jar:10782c593b7edcaf63cf79f7179c4652fee1c01298e0d81d888eea5ea1c320d4',

briar-android/witness.gradle

 dependencyVerification {
     verify = [
-        'Android:Sdk:platforms:android.jar:d20853d289a5161d9cf1c1268d7923076487d4fa68c970b0733e2d5a0ccfc3c5',
         'android.arch.core:common:1.1.0:common-1.1.0.jar:d34824b794bc92ff8f647a9bb13a7c73de920de5b47075b5d2c4f0770e9b8bfd',
         'android.arch.core:runtime:1.1.0:runtime-1.1.0.aar:83400f7575bcfb8a2eeec64e05590f037bfaed1e56aa3a4214d20e55878445e3',
         'android.arch.lifecycle:common:1.1.0:common-1.1.0.jar:614e31cfd33255dc4d5f5d8e62cfa6be2fbbc2a35643a79dc3ed008004c30807',