Upgrade version.androidx.work - AppTP should not specify a different version as that is not used (duckduckgo#2873)

Task/Issue URL:
https://app.asana.com/0/1202552961248957/1201421366311638/f

### Description
Removed different work manager version from vpn-impl.

### Steps to test this PR

Develop
- [ ] Checkout from develop, sync project with gradle files.
- [ ] Look at the androidx.work versions used `./gradlew
app:dependencies | grep androidx.work:work-multiprocess:` and notice
`androidx.work:work-multiprocess:2.5.0-beta01 -> 2.7.1` in the results.

This branch
- [ ] Checkout from this branch, sync project with gradle files.
- [ ] Look at the androidx.work versions used `./gradlew
app:dependencies | grep androidx.work:work-multiprocess:` and notice
only 2.7.1 is used.

### NO UI changes

Author: anikiki

app-tracking-protection/vpn-impl/build.gradle

@@ -38,10 +38,6 @@ android {
     }
 }
 
-ext {
-    workManager = "2.5.0-beta01"
-}
-
 dependencies {
     anvil project(path: ':anvil-compiler')
     implementation project(path: ':anvil-annotations')
@@ -113,7 +109,7 @@ dependencies {
 
     // WorkManager
     implementation AndroidX.work.runtimeKtx
-    implementation "androidx.work:work-multiprocess:$workManager"
+    implementation "androidx.work:work-multiprocess:_"
     testImplementation AndroidX.work.testing
     implementation AndroidX.work.rxJava2