Make sure the deprecated kSdfScopeDelimiter still works

[azeey]

🦟 Bug fix

Summary

The deprecated kSdfScopeDelimiter was initialized to an empty string instead of ::. This PR makes sure kSdfScopeDelimiter and kScopeDelimiter represent the same string.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #1305 (afc4b80) into main (9fc8150) will not change coverage.
The diff coverage is 100.00%.

❗ Current head afc4b80 differs from pull request most recent head 44226e1. Consider uploading reports for the commit 44226e1 to get more accurate results

@@           Coverage Diff           @@
##             main    #1305   +/-   ##
=======================================
  Coverage   87.60%   87.60%           
=======================================
  Files         128      128           
  Lines       16830    16830           
=======================================
  Hits        14744    14744           
  Misses       2086     2086           

Files Changed	Coverage Δ
src/Types.cc	100.00% <100.00%> (ø)