client: fix signing algorithm

[fedekunze]

Description

closes: #6402

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

[codecov]

Codecov Report

Merging #6405 into master will increase coverage by 0.00%.
The diff coverage is 85.71%.

@@           Coverage Diff           @@
##           master    #6405   +/-   ##
=======================================
  Coverage   55.54%   55.54%           
=======================================
  Files         465      465           
  Lines       27515    27524    +9     
=======================================
+ Hits        15284    15289    +5     
- Misses      11133    11136    +3     
- Partials     1098     1099    +1     

[alexanderbez]

ACK

[alessio]

Left small suggestions - though this is good to go already