Revert "Add signing config"

This reverts commit 27e20030e2.
Revert to be able to use gradle without keystore file.

.gitignore

@@ -7,6 +7,4 @@
 /captures
 .externalNativeBuild
 
-/keystore.properties
-
 /app/src/main/assets/sia

app/build.gradle

@@ -9,21 +9,10 @@ android {
         versionCode 3020
         versionName "0.3.2"
     }
-    signingConfigs {
-        def keystoreProperties = new Properties()
-        keystoreProperties.load(new FileInputStream(rootProject.file("keystore.properties")))
-        release {
-            storeFile file(keystoreProperties['storeFile'])
-            storePassword keystoreProperties['storePassword']
-            keyAlias keystoreProperties['keyAlias']
-            keyPassword keystoreProperties['keyPassword']
-        }
-    }
     buildTypes {
         release {
             minifyEnabled false
             proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
-            signingConfig signingConfigs.release
         }
     }
     compileOptions {