process: Proposed ↦ Complete

Amend CI script to new statuses and update existing status field values
in table and BIPs.

```
sed -z -i 's/Status: Proposed/Status: Complete/' bip-0*.md
sed -z -i 's/Status: Proposed/Status: Complete/' bip-0*.mediawiki
sed -i 's/| Proposed/| Complete/' README.mediawiki
```

scripts/buildtable.pl

@@ -72,7 +72,7 @@ my %ValidLayer = (
 my %ValidStatus = (
 	Draft => undef,
 	Deferred => undef,
-	Proposed => "background-color: #ffffcf",
+	Complete => "background-color: #ffffcf",
 	Rejected => "background-color: #ffcfcf",
 	Withdrawn => "background-color: #ffcfcf",
 	Final => "background-color: #cfffcf",