chore: fix typos in comments (#5094)

Signed-off-by: luozexuan <fetchcode@139.com>

src/test/csf/README.md

@@ -144,7 +144,7 @@ sim.collectors.add(simDur);
 ```
 
 The next lines add a single collector to the simulation.  The
-`SimDurationCollector` is a a simple example collector which tracks the total
+`SimDurationCollector` is a simple example collector which tracks the total
 duration of the simulation.  More generally, a collector is any class that
 implements `void on(NodeID, SimTime, Event)` for all [Events](./events.h)
 emitted by a Peer.  Events are arbitrary types used to indicate some action or

src/test/csf/random.h

@@ -121,7 +121,7 @@ makeSelector(Iter first, Iter last, std::vector<double> const& w, Generator& g)
 }
 
 //------------------------------------------------------------------------------
-// Additional distributions of interest not defined in in <random>
+// Additional distributions of interest not defined in <random>
 
 /** Constant "distribution" that always returns the same value
  */

src/test/ledger/Directory_test.cpp

@@ -29,7 +29,7 @@ namespace test {
 
 struct Directory_test : public beast::unit_test::suite
 {
-    // Map [0-15576] into a a unique 3 letter currency code
+    // Map [0-15576] into a unique 3 letter currency code
     std::string
     currcode(std::size_t i)
     {