Correct error return type of Client.connect()

`ConnectTcpError` is a subset of `ConnectError`, but the 4 additional
errors that `ConnectError` comes with:
```zig
error{
    UnsupportedUriScheme,
    UriMissingHost,
    UriHostTooLong,
    CertificateBundleLoadFailure,
}
```
...are never returned by `Client.connect()`. So we are communicating
that this method could return 1 of those 4 types, when in reality, it
never can. This commit fixes this communication error.

Author: joshua-holmes

lib/std/http/Client.zig

@@ -1576,7 +1576,7 @@ pub fn connect(
     host: []const u8,
     port: u16,
     protocol: Protocol,
-) ConnectError!*Connection {
+) ConnectTcpError!*Connection {
     const proxy = switch (protocol) {
         .plain => client.http_proxy,
         .tls => client.https_proxy,