[lldb][NFC] Remove unnecessary lldb_enable_attach in TestMultilineCompletion

We don't actually need to call this for this test.

llvm-svn: 370623

lldb/packages/Python/lldbsuite/test/commands/expression/multiline-completion/main.c

@@ -1,5 +1,4 @@
 int main(int argc, char **argv) {
-  lldb_enable_attach();
   int to_complete = 0;
   return to_complete;
 }