CI: Use matrix.runtime.uri for try-runtime tests

[bkontur]

Some tests gated with the try-runtime feature have the ability to configure the node URI using some hard-coded defaults, e.g.:

let transport: Transport =
			var("WS").unwrap_or("wss://rpc.dotters.network/kusama".to_string()).into();
...
let transport: Transport =
			var("WS").unwrap_or("wss://kusama-rpc.polkadot.io:443".to_string()).into();
...
let transport: Transport =
			var("WS").unwrap_or("wss://rpc.polkadot.io:443".to_string()).into();
...
let transport: Transport =
			var("WS").unwrap_or("wss://rpc.dotters.network/polkadot".to_string()).into();

Additionally, we have a dedicated runtime uri specified in the runtimes-matrix.json, e.g.,

{
    "name": "polkadot",
    "uri": "wss://try-runtime.polkadot.io:443",
  },
  {
    "name": "kusama",
    "uri": "wss://try-runtime-kusama.polkadot.io:443",
  },

so, let's use those dedicated uris instead of the hard-coded ones.

---

I came across this issue by accident when Kusama's remote_tests::next_inflation failed with Error while getting storage data here: https://github.com/polkadot-fellows/runtimes/actions/runs/12526255825/job/34938624858?pr=519.
I wasn't sure if it is flaky, missing some keys in the actual block, or just a connection problem, so I also enabled remote-ext=info logs (if the logs are too much, we can switch to remote-ext=warn/error).

remote_tests::next_inflation --- FAILED

failures:

---- remote_tests::next_inflation stdout ----
thread 'remote_tests::next_inflation' panicked at relay/kusama/src/lib.rs:3230:14:
called `Result::unwrap()` on an `Err` value: "Error while getting storage data"

• Does not require a CHANGELOG entry

[bkchr]

/merge

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