Set BreakConstructorInitializers to BeforeComma

The initialization list will be of this form:
Class::Class()
    : var1(...)
    , var2(...)
{}

instead of
Class::Class()
    : var1(...),
      var2(...)
{}

.clang-format

@@ -31,7 +31,7 @@ BraceWrapping:
   SplitEmptyRecord: true
 BreakBeforeBinaryOperators: NonAssignment
 BreakBeforeTernaryOperators: true
-BreakConstructorInitializers: BeforeColon
+BreakConstructorInitializers: BeforeComma
 BreakInheritanceList: BeforeColon
 ColumnLimit: 100
 CompactNamespaces: false