Bump mixin from 0.7.11-SNAPSHOT to 0.8.2

Bumps [mixin](https://github.com/SpongePowered/Mixin) from 0.7.11-SNAPSHOT to 0.8.2.
- [Release notes](https://github.com/SpongePowered/Mixin/releases)
- [Commits](https://github.com/SpongePowered/Mixin/commits/releases/0.8.2)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

build.gradle

@@ -37,7 +37,7 @@ compileJava.options.encoding = 'UTF-8'
 
 dependencies {
     // Enabled me only for build
-    annotationProcessor 'org.spongepowered:mixin:0.7.11-SNAPSHOT'
+    annotationProcessor 'org.spongepowered:mixin:0.8.2'
     compile('org.spongepowered:mixin:0.7.11-SNAPSHOT') {
         // Mixin includes a lot of dependencies that are too up-to-date
         exclude module: 'guava'