build(deps): bump golang.org/x/sync from 0.19.0 to 0.21.0 (#1204)

Bumps [golang.org/x/sync](https://github.com/golang/sync) from 0.19.0 to
0.21.0.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/golang/sync/commit/5071ed6a9f1617117556b66384f765c934de3698"><code>5071ed6</code></a>
all: fix some comments to improve readability</li>
<li><a
href="https://github.com/golang/sync/commit/ec11c4a93de22cde2abe2bf74d70791033c2464c"><code>ec11c4a</code></a>
errgroup: fix a typo in the documentation</li>
<li><a
href="https://github.com/golang/sync/commit/1a583072c11b16c643c8f6051ff1fab5a424d0a9"><code>1a58307</code></a>
all: modernize interface{} -&gt; any</li>
<li><a
href="https://github.com/golang/sync/commit/3172ca581eb96530283f713311f81df986c19932"><code>3172ca5</code></a>
all: upgrade go directive to at least 1.25.0 [generated]</li>
<li>See full diff in <a
href="https://github.com/golang/sync/compare/v0.19.0...v0.21.0">compare
view</a></li>
</ul>
</details>
<br />

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

go.mod

@@ -5,7 +5,7 @@ go 1.25.0
 require (
 	github.com/opencontainers/go-digest v1.0.0
 	github.com/opencontainers/image-spec v1.1.1
-	golang.org/x/sync v0.19.0
+	golang.org/x/sync v0.21.0
 )
 
 require github.com/BurntSushi/toml v1.6.0

go.sum

@@ -4,5 +4,5 @@ github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8
 github.com/opencontainers/go-digest v1.0.0/go.mod h1:0JzlMkj0TRzQZfJkVvzbP0HBR3IKzErnv2BNG4W4MAM=
 github.com/opencontainers/image-spec v1.1.1 h1:y0fUlFfIZhPF1W537XOLg0/fcx6zcHCJwooC2xJA040=
 github.com/opencontainers/image-spec v1.1.1/go.mod h1:qpqAh3Dmcf36wStyyWU+kCeDgrGnAve2nCC8+7h8Q0M=
-golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=
-golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
+golang.org/x/sync v0.21.0 h1:HLII4xRRTtCRkxYp4HNFF0Js/Og6q2i++KXbg0gHCwM=
+golang.org/x/sync v0.21.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=