Include logback12 from logback module (#5139)

Motivation:

@ikhoon pointed out that the `logback` module doesn't bring in the
`logback12` module in the pom.

Modifications:

- Modified so that the `logback` module correctly declares the
dependency.

Result:

- `logback` module contains the correct dependencies
- Describe the consequences that a user will face after this PR is
merged.

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logback/logback/build.gradle

@@ -1,4 +1,4 @@
 dependencies {
     // Logback
-    api libs.logback12
+    api project(':logback12')
 }