Fix formating for passrate

Related-Prod: PRODX-48948

Change-Id: If910435f5ea010fe226a3638a9a8f9e5cd24ddef
diff --git a/rp_reporter/rp_reporter/report_from_xml.py b/rp_reporter/rp_reporter/report_from_xml.py
index 5b38e6a..6dcb7c7 100644
--- a/rp_reporter/rp_reporter/report_from_xml.py
+++ b/rp_reporter/rp_reporter/report_from_xml.py
@@ -76,9 +76,9 @@
 
     def __repr__(self):
         if self.passrate < 100:
-            passrate = "`{self.passrate:.2f}%`"
+            passrate = f"`{self.passrate:.2f}%`"
         else:
-            passrate = "{self.passrate:.2f}%"
+            passrate = f"{self.passrate:.2f}%"
         return f"P{self.passed}/F{self.failed}/E{self.errors} {passrate}"
 
 class Reporter: