roachtest: remove error assertion from panic node mutator

The panic node mutator error assertion is causing flakes, as the error is not
always the specific TCP error that is expected even if the panic is working as
it should.

Given that we are not testing the panic implementation here, asserting on the
node being down should be enough.

Epic: None
Release note: None

Author: herkolategan

pkg/cmd/roachtest/roachtestutil/mixedversion/steps.go

@@ -10,7 +10,6 @@ import (
 	"fmt"
 	"math"
 	"math/rand"
-	"regexp"
 	"strings"
 	"time"
 
@@ -804,8 +803,6 @@ func (s panicNodeStep) Description() string {
 	return fmt.Sprintf("panicking system interface on node %d", s.targetNode[0])
 }
 
-var connectionRefusedRegex = regexp.MustCompile(`dial tcp .*: connect: connection refused`)
-
 func (s panicNodeStep) Run(ctx context.Context, l *logger.Logger, rng *rand.Rand, h *Helper) error {
 	nodeVersion, err := h.System.NodeVersion(s.targetNode[0])
 	if err != nil {
@@ -831,14 +828,6 @@ func (s panicNodeStep) Run(ctx context.Context, l *logger.Logger, rng *rand.Rand
 		return errors.Errorf("expected panic statement to fail, but it succeeded on %s", s.targetNode)
 	}
 
-	isTCPError := connectionRefusedRegex.MatchString(err.Error())
-
-	// The expected behavior is that the panic statement will fail with a TCP connection error,
-	// so any other error is unexpected and should cause the test to fail.
-	if !isTCPError {
-		return errors.Wrapf(err, "unexpected error when executing panic statement on %s", s.targetNode)
-	}
-
 	startCtx, cancel := context.WithTimeout(ctx, startTimeout)
 	defer cancel()