Switch http to https in banner

[rgwood]

Changing http to https in the banner now that https://nushell.sh works: nushell/nushell.github.io#294

[codecov]

Codecov Report

Merging #8272 (fcb9867) into main (27d7982) will decrease coverage by 0.38%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8272      +/-   ##
==========================================
- Coverage   68.09%   67.71%   -0.38%     
==========================================
  Files         621      621              
  Lines       99312    99312              
==========================================
- Hits        67628    67254     -374     
- Misses      31684    32058     +374     

Impacted Files	Coverage Δ
crates/nu-cli/src/repl.rs	24.42% <0.00%> (ø)
crates/nu-color-config/src/nu_style.rs	9.31% <0.00%> (-70.92%)	⬇️
crates/nu-parser/src/lite_parser.rs	67.18% <0.00%> (-2.17%)	⬇️
crates/nu-parser/src/parser.rs	82.55% <0.00%> (+0.09%)	⬆️
src/test_bins.rs	96.88% <0.00%> (+0.44%)	⬆️