[dynatraceexporter] Update Changelog entry to be breaking instead (op…

…en-telemetry#12351)

* Update Changelog entry to be breaking instead

* add "cumulative"

unreleased/dt-updates.yaml

@@ -1,5 +1,5 @@
 # One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
-change_type: enhancement
+change_type: breaking
 
 # The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
 component: dynatraceexporter
@@ -12,4 +12,5 @@ issues: [ 11828 ]
 
 # (Optional) One or more lines of additional information to render under the primary note.
 # These lines will be padded with 2 spaces and then inserted directly into the document.
-subtext:
+subtext: |2
+ - Non-monotonic cumulative Sum metrics will be exported as Gauges from now on. Non-monotonic cumulative Sums (usually UpDownCounters) will show the current value instead of a change rate.