fix: revert tabs in documentation.md.tmpl YAML code blocks

documentation.md.tmpl contains YAML code examples (enabled: true/false
inside metric/event config snippets) that are emitted verbatim into the
generated documentation.md files. Tab indentation in those snippets
caused make gogenerate to produce tabs in the output, failing the
'Generated code is out of date' diff check.

Only Go template files (.go.tmpl) should use tab indentation.

Assisted-by: Claude Sonnet 4.6

Author: Goutham-Annem

cmd/mdatagen/internal/templates/documentation.md.tmpl

@@ -154,7 +154,7 @@ The following metrics are emitted by default. Each of them can be disabled by ap
 ```yaml
 metrics:
   <metric_name>:
-	enabled: false
+    enabled: false
 ```
 
 {{- end }}
@@ -179,7 +179,7 @@ The following metrics are not emitted by default. Each of them can be enabled by
 ```yaml
 metrics:
   <metric_name>:
-	enabled: true
+    enabled: true
 ```
 
 {{- end }}
@@ -199,7 +199,7 @@ The following events are emitted by default. Each of them can be disabled by app
 ```yaml
 events:
   <event_name>:
-	enabled: false
+    enabled: false
 ```
 
 {{- range $eventName, $event := .Events }}
@@ -223,7 +223,7 @@ The following events are not emitted by default. Each of them can be enabled by
 ```yaml
 events:
   <event_name>:
-	enabled: true
+    enabled: true
 ```
 
 {{- end }}