fix: change www.lua.org to lua.org to reflect certificate change

[vpayno]

Looks like https://lua.org/ 's certificate changed today.

* Server certificate:                                                                                                                                                       *  subject: CN=lua.org                                                                                                                                                      *  start date: Dec 20 17:54:42 2023 GMT
*  expire date: Mar 19 17:54:41 2024 GMT
*  subjectAltName: host "lua.org" matched cert's "lua.org"
*  issuer: C=US; O=Let's Encrypt; CN=R3
*  SSL certificate verify ok.

Run leafo/gh-actions-lua@v10
  with:
    luaVersion: 5.4
    buildCache: true
Notice: gh-actions-lua: No cache available, clean build
Hostname/IP does not match certificate's altnames: Host: www.lua.org. is not in the cert's altnames: DNS:lua.org
Waiting 18 seconds before trying again
Hostname/IP does not match certificate's altnames: Host: www.lua.org. is not in the cert's altnames: DNS:lua.org
Waiting 1[6](https://github.com/vpayno/exercism-workspace/actions/runs/7284425228/job/19849762432?pr=323#step:3:7) seconds before trying again
Error: Failed to install

[vpayno]

Tested this fix, it works.

--- a/.github/workflows/lua.yml
+++ b/.github/workflows/lua.yml
@@ -63,7 +63,7 @@ jobs:
         uses: actions/checkout@v3
       - name: Set up Lua
         id: setup-lua
-        uses: leafo/gh-actions-lua@v10
+        uses: vpayno/gh-actions-lua@fix_cert_url
         with:
           luaVersion: ${{ matrix.luaVersion }}
       - name: Show Lua Versions

[hishamhm]

@leafo I've also loaded this change when testing the CI runs for luasystem at lunarmodules/luasystem#17 and all went well.