fix: remove redundant test typecheck step from CI

The separate tsc typecheck for tests was failing due to issues with
Speakeasy-generated funcs files. This step is redundant since:
- pnpm run build already type-checks the source
- vitest handles type-checking when running tests

Author: mattapperson

.github/actions/validate-sdk/action.yaml

@@ -28,10 +28,6 @@ runs:
       shell: bash
       run: pnpm run build
 
-    - name: Typecheck tests directory
-      shell: bash
-      run: pnpm exec tsc --noEmit --skipLibCheck --esModuleInterop --moduleResolution node --module esnext --target es2020 tests/**/*.ts
-
     - name: Install examples dependencies
       shell: bash
       working-directory: examples