[release-branch.go1.18] text/template/parse: allow space after continue or break

[release-branch.go1.18] text/template/parse: allow space after continue or break

Trivial fix: We must skip space after either of these keywords
before we expect a closing delimiter.

Also delete the stutter-generating extra 'in' in the error message.
(See what I did there?)

For #51670
Fixes #52878

Change-Id: If5415632c36eaac6699bdc0aa6ce18be956c9b53
Reviewed-on: https://go-review.googlesource.com/c/go/+/392615
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Trust: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gopher Robot <gobot@golang.org>
(cherry picked from commit 41a82aa9c36bffab2593d50aa55a462fef4e5bd4)
Reviewed-on: https://go-review.googlesource.com/c/go/+/406074
Reviewed-by: Alex Rakoczy <alex@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>