Bump r2dbc-mariadb from 0.8.1-alpha1 to 0.8.2-alpha2 in /modules/mariadb (#2702)

Author: dependabot-preview[bot]

modules/mariadb/build.gradle

@@ -7,7 +7,7 @@ dependencies {
     compile project(':jdbc')
 
     compileOnly project(':r2dbc')
-    compileOnly 'org.mariadb:r2dbc-mariadb:0.8.1-alpha1'
+    compileOnly 'org.mariadb:r2dbc-mariadb:0.8.2-alpha2'
 
     testCompile project(':jdbc-test')
     testCompile 'org.mariadb.jdbc:mariadb-java-client:2.6.0'