tree-wide: drop duplicated blank lines

```
$ for i in */*.[ch] */*/*.[ch]; do sed -e '/^$/ {N; s/\n$//g}' -i $i; done
$ git checkout HEAD -- basic/linux shared/linux
```

src/shared/bus-wait-for-units.c

@@ -366,7 +366,6 @@ int bus_wait_for_units_add_unit(
                 if (r < 0)
                         return log_debug_errno(r, "Failed to add reference to unit %s: %m", unit);
 
-
                 item->flags |= BUS_WAIT_REFFED;
         }
 

src/shared/journal-importer.c

@@ -23,7 +23,6 @@ enum {
         IMPORTER_STATE_EOF,         /* done */
 };
 
-
 void journal_importer_cleanup(JournalImporter *imp) {
         if (imp->fd >= 0 && !imp->passive_fd) {
                 log_debug("Closing %s (fd=%d)", imp->name ?: "importer", imp->fd);

src/shared/logs-show.c

@@ -431,7 +431,6 @@ static int output_short(
         if (priority_len == 1 && *priority >= '0' && *priority <= '7')
                 p = *priority - '0';
 
-
         audit = streq_ptr(transport, "audit");
 
         if (mode == OUTPUT_SHORT_MONOTONIC)

src/shared/varlink.c

@@ -1874,7 +1874,6 @@ fail:
         return r;
 }
 
-
 void varlink_detach_event(Varlink *v) {
         if (!v)
                 return;