rego: remove superfluous package import of plugins

Fixes #6754.

The PR message of #5939 indicates that the plugin manager is NOT used
for this. And where was nothing in the code setting `pluginMgr`.

Signed-off-by: Stephan Renatus <stephan.renatus@gmail.com>

Author: srenatus

v1/rego/rego.go

@@ -27,7 +27,6 @@ import (
 	"github.com/open-policy-agent/opa/v1/loader"
 	"github.com/open-policy-agent/opa/v1/loader/filter"
 	"github.com/open-policy-agent/opa/v1/metrics"
-	"github.com/open-policy-agent/opa/v1/plugins"
 	"github.com/open-policy-agent/opa/v1/resolver"
 	"github.com/open-policy-agent/opa/v1/storage"
 	"github.com/open-policy-agent/opa/v1/storage/inmem"
@@ -666,8 +665,6 @@ type Rego struct {
 	enablePrintStatements       bool
 	distributedTracingOpts      tracing.Options
 	strict                      bool
-	pluginMgr                   *plugins.Manager
-	plugins                     []TargetPlugin
 	targetPrepState             TargetPluginEval
 	regoVersion                 ast.RegoVersion
 	compilerHook                func(*ast.Compiler)
@@ -1428,15 +1425,6 @@ func New(options ...func(r *Rego)) *Rego {
 		r.generateJSON = generateJSON
 	}
 
-	if r.pluginMgr != nil {
-		for _, pluginName := range r.pluginMgr.Plugins() {
-			p := r.pluginMgr.Plugin(pluginName)
-			if p0, ok := p.(TargetPlugin); ok {
-				r.plugins = append(r.plugins, p0)
-			}
-		}
-	}
-
 	if t := r.targetPlugin(r.target); t != nil {
 		r.compiler = r.compiler.WithEvalMode(ast.EvalModeIR)
 	}