test: Remove new grep warning

With newer versions of grep, you now see:

	grep: warning: stray \ before "

This is because we had an erroneous backslash escaping a quote. Remove
it.

test/test-govet.sh

@@ -60,10 +60,10 @@ function naked-error() {
 
 # catch errors that start with a capital
 function lowercase-errors() {
- if grep -E 'errors\.New\(\"[A-Z]' "$1"; then
+ if grep -E 'errors\.New\("[A-Z]' "$1"; then
  return 1
  fi
- if grep -E 't\.Errorf\(\"[A-Z]' "$1"; then # t.Errorf or fmt.Errorf
+ if grep -E 't\.Errorf\("[A-Z]' "$1"; then # t.Errorf or fmt.Errorf
  return 1
  fi
  # TODO: add errwrap.Wrap* related matching