Update logback-core to 1.3.9 (#3105)

## About this PR
📦 Updates
[ch.qos.logback:logback-core](https://github.com/qos-ch/logback) from
`1.3.8` to `1.3.9`

## Usage
✅ **Please merge!**

I'll automatically update this PR to resolve conflicts as long as you
don't change it yourself.

If you'd like to skip this version, you can just close this PR. If you
have any feedback, just mention me in the comments below.

Configure Scala Steward for your repository with a
[`.scala-steward.conf`](https://github.com/scala-steward-org/scala-steward/blob/b83aae55d9dd000548c3b3c9b63d79636e7b3c8b/docs/repo-specific-configuration.md)
file.

_Have a fantastic day writing Scala!_

<details>
<summary>🔍 Files still referring to the old version number</summary>

The following files still refer to the old version number (1.3.8).
You might want to review and update them manually.
```
docs/release-notes.md
```
</details>
<details>
<summary>⚙ Adjust future updates</summary>

Add this to your `.scala-steward.conf` file to ignore future updates of
this dependency:
```
updates.ignore = [ { groupId = "ch.qos.logback", artifactId = "logback-core" } ]
```
Or, add this to slow down future updates of this dependency:
```
dependencyOverrides = [{
  pullRequests = { frequency = "30 days" },
  dependency = { groupId = "ch.qos.logback", artifactId = "logback-core" }
}]
```
</details>

<sup>
labels: library-update
</sup>

airspec/build.sbt

@@ -128,8 +128,7 @@ def excludePomDependency(excludes: Seq[String]) = { node: XmlNode =>
   }).transform(node).head
 }
 
-/**
-  * AirSpec build definitions.
+/** AirSpec build definitions.
   *
   * To make AirSpec a standalone library without any cyclic project references, AirSpec embeds the source code of
   * airframe-log, di, surface, etc.
@@ -213,7 +212,7 @@ lazy val airspecLog =
       airspecJVMBuildSettings,
       libraryDependencies ++= Seq(
         // For rotating log files
-        "ch.qos.logback" % "logback-core" % "1.3.8"
+        "ch.qos.logback" % "logback-core" % "1.3.9"
       )
     )
     .jsSettings(

build.sbt

@@ -527,7 +527,7 @@ val logDependencies = { scalaVersion: String =>
 
 val logJVMDependencies = Seq(
   // For rotating log files
-  "ch.qos.logback" % "logback-core" % "1.3.8"
+  "ch.qos.logback" % "logback-core" % "1.3.9"
 )
 
 // airframe-log should have minimum dependencies