[CI][Benchmarks] Correct no explicit_group warning (#19397)

It is fine that some benchmark metadata does not have explicit_group
defined. Change a misleading warning.

Example of a series of warnings on explicit_group missing:
https://github.com/oneapi-src/unified-runtime/actions/runs/16182812320/job/45685586721#step:14:2048

Author: PatKamin

devops/scripts/benchmarks/output_markdown.py

@@ -115,18 +115,13 @@ def is_content_in_size_limit(content_size: int, current_markdown_size: int):
 
 
 def get_explicit_group_name(result: Result, metadata: dict[str, BenchmarkMetadata]):
-    explicit_group_name = ""
     try:
-        explicit_group_name = metadata[result.label].explicit_group
-    except Exception as e:
-        log.warning(
-            f"Unexpected error when getting explicit_group for '{result.label}': {e}"
-        )
+        group_name = metadata[result.label].explicit_group
+        return group_name if group_name else "Other"
+    except Exception:
+        log.debug(f"No explicit group found for {result.label}, using 'Other'")
         return "Other"
 
-    return explicit_group_name if explicit_group_name else "Other"
-
-
 # Function to generate the markdown collapsible sections for each variant
 def generate_markdown_details(
     results: list[Result], current_markdown_size: int, markdown_size: MarkdownSize