sdk/trace: remove unused version function (#7036)

The unexported `version()` function in `sdk/trace` is not used anywhere.
Not mentioning that the value it is returning is wrong.

There is already a `Version` function in `sdk` (which is in the same Go
module).

sdk/trace/version.go

@@ -1,9 +0,0 @@
-// Copyright The OpenTelemetry Authors
-// SPDX-License-Identifier: Apache-2.0
-
-package trace // import "go.opentelemetry.io/otel/sdk/trace"
-
-// version is the current release version of the metric SDK in use.
-func version() string {
-	return "1.16.0-rc.1"
-}

sdk/trace/version_test.go

@@ -1,21 +0,0 @@
-// Copyright The OpenTelemetry Authors
-// SPDX-License-Identifier: Apache-2.0
-
-package trace
-
-import (
-	"regexp"
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-)
-
-var versionRegex = regexp.MustCompile(`^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)` +
-	`(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)` +
-	`(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?` +
-	`(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$`)
-
-func TestVersionSemver(t *testing.T) {
-	v := version()
-	assert.Regexp(t, versionRegex, v)
-}