Remove nonsensical fct definition

Aggregation's getvalue function has a nonsensical definition and is thus
not used by anything. This commit removes it.

Reviewed By: tnfchris

Differential Revision: https://reviews.llvm.org/D94838

Author: Thomas Preud'homme

lnt/server/reporting/summaryreport.py

@@ -14,9 +14,6 @@ def __init__(self):
     def __repr__(self):
         return repr(self.getvalue())
 
-    def getvalue(self):
-        abstract
-
     def append(self, values):
         if not self.is_initialized:
             self.is_initialized = True