Deps: Add google flexbox transitively used dependencies on wordpress

It is generally recommended that transitively used dependencies should
be declared directly.

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Actually, updating 'Zendesk', which was the dependency that was
providing this transitively used 'Flexbox' dependency to the project,
was causing a compilation failure. This is due to the fact that the
[BloggingPromptsOnboardingDialogFragment],
[BloggingPromptCardViewHolder] and [WPEditTextWithChipsOutlined] classes
are directly using this dependency, but could no longer resolve it.

PS: This is (most probably) due to the fact that this 'Flexbox'
dependency was no longer available on newer 'Zendesk' versions.

WordPress/build.gradle

@@ -389,6 +389,7 @@ dependencies {
     implementation "androidx.cardview:cardview:$androidxCardviewVersion"
     implementation "androidx.recyclerview:recyclerview:$androidxRecyclerviewVersion"
     implementation "com.google.android.material:material:$googleMaterialVersion"
+    implementation "com.google.android.flexbox:flexbox:$googleFlexboxlayoutVersion"
     implementation "androidx.percentlayout:percentlayout:$androidxPercentlayoutVersion"
     implementation "androidx.swiperefreshlayout:swiperefreshlayout:$androidxSwipeToRefreshVersion"
     implementation "androidx.preference:preference:$androidxPreferenceVersion"

build.gradle

@@ -64,6 +64,7 @@ ext {
     glideVolleyVersion = '4.6.1@aar'
     googleAutoServiceVersion = '1.0'
     googleExoPlayerVersion = '2.13.3'
+    googleFlexboxlayoutVersion = '3.0.0'
     googleGsonVersion = '2.6.2'
     googleMaterialVersion = '1.2.1'
     googleMLKitBarcodeScanningVersion = '17.0.0'