Remove double spaces from comments and documentation.

Double spaces have fallen out of favor in recent years because they no longer contribute to readability.

We have been using single spaces and editing related paragraphs for some time, but now it seems best to update the remaining instances to avoid churn in unrelated commits and to make it clearer what spacing contributors should use.

test/lib/pgBackRestTest/Common/Io/Buffered.pm

@@ -100,7 +100,7 @@ sub read
         $iRemainingSize -= $iReadSize;
     }
 
-    # If this is a blocking read then loop until all bytes have been read, else error.  If not blocking read until the request size
+    # If this is a blocking read then loop until all bytes have been read, else error. If not blocking read until the request size
     # has been met or EOF.
     my $fTimeStart = gettimeofday();
     my $fRemaining = $self->timeout();
@@ -264,7 +264,7 @@ sub handleReadSet
     $self->{oReadSelect} = IO::Select->new();
     $self->{oReadSelect}->add($self->handleRead());
 
-    # Check if the read handle has a pending method.  This should be checked before can_read for SSL sockets.
+    # Check if the read handle has a pending method. This should be checked before can_read for SSL sockets.
     $self->{bPending} = defined($fhRead) && $fhRead->can('pending') ? true : false;
 }