Fix duplicate word in SBOM generator description

Removes the duplicate word "is" from "By default, it uses is the"
so it reads "By default, it uses the".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dvdksn

content/manuals/build/metadata/attestations/sbom.md

@@ -202,7 +202,7 @@ base-passwd@3.5.47
 
 ## SBOM generator
 
-BuildKit generates the SBOM using a scanner plugin. By default, it uses is the
+BuildKit generates the SBOM using a scanner plugin. By default, it uses the
 [BuildKit Syft scanner](https://github.com/docker/buildkit-syft-scanner)
 plugin. This plugin is built on top of
 [Anchore's Syft](https://github.com/anchore/syft),