Bump sigstore from 0.6.2 to 0.6.3 in /requirements

Bumps [sigstore](https://github.com/sigstore/sigstore-python) from 0.6.2 to 0.6.3.
- [Release notes](https://github.com/sigstore/sigstore-python/releases)
- [Commits](sigstore/sigstore-python@v0.6.2...v0.6.3)

---
updated-dependencies:
- dependency-name: sigstore
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements/publish.txt

@@ -122,10 +122,6 @@ packaging==21.3 \
     --hash=sha256:dd47c42927d89ab911e606518907cc2d3a1f38bbd026385970643f9c5b8ecfeb \
     --hash=sha256:ef103e05f519cdc783ae24ea4e2e0f508a9c99b2d4969652eed6a2e1ea5bd522
     # via build
-pem==21.2.0 \
-    --hash=sha256:64afb669f05502c071d0706ee66e51471718ae248ba39624919da7b4ea73506e \
-    --hash=sha256:c491833b092662626fd58a87375d450637d4ee94996ad9bbbd42593428e93e5a
-    # via sigstore
 pep517==0.12.0 \
     --hash=sha256:931378d93d11b298cf511dd634cf5ea4cb249a28ef84160b3247ee9afb4e8ab0 \
     --hash=sha256:dd884c326898e2c6e11f9e0b64940606a93eb10ea022a2e067959f3a110cf161
@@ -203,9 +199,9 @@ securesystemslib==0.23.0 \
     --hash=sha256:573e9c810f2a6afe9ac71a177f26b9d6a321c53574f561f5cef2ed511c3f1831 \
     --hash=sha256:613c2891a8b4480bae6edb2351710f8c695679101ea7f471cc56f64980d2cd38
     # via sigstore
-sigstore==0.6.2 \
-    --hash=sha256:6f21b16fa23fcae8ed3ebfcd691412f597c40172b17dc4191f23b48239f0c498 \
-    --hash=sha256:e560636112dc09d729097adc5a33f154648ed79f1b3d40359736843e0e351d07
+sigstore==0.6.3 \
+    --hash=sha256:e109ecc7a24734215da3627893f0373232637e27688ef0bae4cd6d03ba6e24e5 \
+    --hash=sha256:f51334dc4b4fb025c7ba370183c0933bb465146f5ada8ff5871725bfe583a9ee
     # via -r publish.in
 tomli==2.0.1 \
     --hash=sha256:939de3e7a6161af0c887ef91b7d41a53e7c5a1ca976325f429cb46ea9bc30ecc \