Prune changelogs after 8.19.4 release

docs/changelog/133392.yaml

@@ -1,5 +0,0 @@
-pr: 133392
-summary: Track memory in evaluators
-area: ES|QL
-type: bug
-issues: []

docs/changelog/133848.yaml

@@ -1,5 +0,0 @@
-pr: 133848
-summary: Delay S3 repo warning if default region absent
-area: Snapshot/Restore
-type: bug
-issues: []

docs/changelog/134134.yaml

@@ -1,6 +0,0 @@
-pr: 134134
-summary: Prevent field caps from failing due to can match failure
-area: Search
-type: bug
-issues:
- - 116106

docs/changelog/134253.yaml

@@ -1,5 +0,0 @@
-pr: 134253
-summary: Fixed a bug where text fields in LogsDB indices did not use their keyword multi fields for block loading
-area: Mapping
-type: bug
-issues: []

docs/changelog/134451.yaml

@@ -1,6 +0,0 @@
-pr: 134451
-summary: Use inner query for equals/hashCode() in `SourceConfirmedTextQuery`
-area: "Search"
-type: bug
-issues:
- - 134432

docs/changelog/134711.yaml

@@ -1,5 +0,0 @@
-pr: 134711
-summary: Add Reason field to elastic-agent upgrade details metadata
-area: Infra/Plugins
-type: enhancement
-issues: []