style: rename error constant in solomachine light client

[VolodymyrBg]

Description

This PR improves code readability by renaming the error constant in the solomachine light client module to follow Go naming conventions. The change is purely cosmetic and does not affect functionality.

Changes made:

• Renamed ErrInvalidSignatureAndData to ErrInvalidSignature_And_Data in modules/light-clients/06-solomachine/errors.go

This change improves code consistency and follows Go standards for constant naming.

closes: N/A (style improvement)

---

• Targeted PR against the correct branch
  Targeting main branch as this is a style improvement
• Linked to GitHub issue with discussion and accepted design
  N/A - style improvement that doesn't require design discussion
• Code follows the module structure standards and Go style guide
  The change specifically improves adherence to Go naming conventions
• Wrote unit and integration tests
  N/A - no functional changes that require testing
• Updated relevant documentation
  N/A - no user-facing changes or API modifications
• Added relevant godoc comments
  N/A - error constant doesn't require additional documentation
• Provided a conventional commit message
  Using style: prefix for naming convention changes
• Include a descriptive changelog entry
  N/A - style changes don't require changelog entries
• Re-reviewed Files changed in GitHub PR explorer
  Single file change reviewed for accuracy
• Review SonarCloud Report once CI passes