Update Whats New for v4 (#2821)

* Update upgrading-github-v3-to-v4.md

* Update gitlab as well

* Update upgrading-gitlab-v1-to-v2.md

* Update upgrading-github-v3-to-v4.md

Author: ZachGoldberg

docs/2.0/docs/pipelines/previous-versions/upgrading-github-v3-to-v4.md

@@ -27,6 +27,17 @@ The following [feature flags](https://docs.gruntwork.io/2.0/reference/pipelines/
 * PIPELINES_FEATURE_EXPERIMENT_COLOCATED_FILE_UNIT_CHANGE_DETECTION
 * PIPELINES_FEATURE_EXPERIMENT_MINIMIZE_BLAST_RADIUS
 
+### `--queue-include-units-reading` used instead of `--units-that-include`
+
+Pipelines will now always use `--queue-include-units-reading` instead of `--units-that-include`. 
+
+Previously, Pipelines would only use the former flag for `FileChanged` events for the sake of providing greater backwards compatibility, but the minimum supported version of Terragrunt in Pipelines now supports `--units-that-include`, and this is no longer necessary.
+
+By making this change, Pipelines now behaves more in-line with customer expectations, as customers expect that a file with an `.hcl` extension read via an HCL function like `read_terragrunt_config()` should still result in inclusion into the run queue.
+
+### Updated Terminology: Module -> Unit
+Pipelines now refers to leaf folders with a `terragrunt.hcl` file as `units`.  Prior versions used the term `module`.  This change aligns Pipelines' terminology with Terragrunt's.
+ 
 # Migration Guide
 
 ## Updating Terragrunt Version

docs/2.0/docs/pipelines/previous-versions/upgrading-gitlab-v1-to-v2.md

@@ -27,6 +27,17 @@ The following [feature flags](https://docs.gruntwork.io/2.0/reference/pipelines/
 * PIPELINES_FEATURE_EXPERIMENT_COLOCATED_FILE_UNIT_CHANGE_DETECTION
 * PIPELINES_FEATURE_EXPERIMENT_MINIMIZE_BLAST_RADIUS
 
+### `--queue-include-units-reading` used instead of `--units-that-include`
+
+Pipelines will now always use `--queue-include-units-reading` instead of `--units-that-include`. 
+
+Previously, Pipelines would only use the former flag for `FileChanged` events for the sake of providing greater backwards compatibility, but the minimum supported version of Terragrunt in Pipelines now supports `--units-that-include`, and this is no longer necessary.
+
+By making this change, Pipelines now behaves more in-line with customer expectations, as customers expect that a file with an `.hcl` extension read via an HCL function like `read_terragrunt_config()` should still result in inclusion into the run queue.
+
+### Updated Terminology: Module -> Unit
+Pipelines now refers to leaf folders with a `terragrunt.hcl` file as `units`.  Prior versions used the term `module`.  This change aligns Pipelines' terminology with Terragrunt's.
+ 
 # Migration Guide
 To upgrade Pipelines from v1 to v2, perform the following changes in each
 repository that includes the Gruntwork Pipelines Workflows.