[process list] make the TRIPLE column wider

Summary:
Now that `process list` works better on the android platform, the arch aarch64-unknown-linux-android appears quite often.
The existing printed width of the TRIPLE column is not long enough, which doesn't look okay.
E.g.
```
1561   1016                    aarch64-unknown-linux-android ip6tables-restore
1999   1                       aarch64-unknown-linux-android tlc_server
2332   982                                              com.android.systemui
2378   983                                              webview_zygote
```

Now, after adding 6 spaces, it looks better

```
PID    PARENT USER       TRIPLE                         NAME
====== ====== ========== ============================== ============================
...
1561   1016              aarch64-unknown-linux-android  ip6tables-restore
1999   1                 aarch64-unknown-linux-android  tlc_server
2332   982                                              com.android.systemui
2378   983                                              webview_zygote
2448   982                                              com.sec.location.nsflp2
```

Reviewers: clayborg, labath, xiaobai, aadsm

Reviewed By: labath

Subscribers: srhines, kristof.beyls, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D68291

llvm-svn: 373670