Bump gradle from 1.25.4 to 1.26.0 (#1014)

Bumps gradle from 1.25.4 to 1.26.0.

Signed-off-by: dependabot[bot] <support@dependabot.com>

mobile/build.gradle

@@ -12,7 +12,7 @@ buildscript {
     }
     dependencies {
         classpath 'com.google.gms:google-services:4.1.0'
-        classpath 'io.fabric.tools:gradle:1.25.4'
+        classpath 'io.fabric.tools:gradle:1.26.0'
         classpath files('libs/gradle-witness.jar')
     }
 }