process: Standards Track ↦ Specification

```
sed -z -i 's/Type: Standards Track/Type: Specification/' bip-0*.md
sed -z -i 's/Type: Standards Track/Type: Specification/' bip-0*.mediawiki
```

After the scripted changes, the changes to BIP-40, BIP-41, and BIP-63
were undone, because it breaks CI.

These three BIPs only exist conceptually and their proposal documents
are missing which causes changes to them ot break the CI. I defer the
changes to these BIPs to a separate pull request to get CI to pass.

scripts/buildtable.pl

@@ -76,7 +76,7 @@ my %ValidStatus = (
 	Closed => "background-color: #ffcfcf",
 );
 my %ValidType = (
-	'Standards Track' => 'Standard',
+	'Specification' => undef,
 	'Informational' => undef,
 	'Process' => undef,
 );