[easy doc] Remove redundant info in README.valgrind

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-07-28.18:07:12.899>
labels = ['3.11', 'type-feature', 'docs']
title = '[easy doc] Remove redundant info in README.valgrind'
updated_at = <Date 2021-07-31.15:02:13.673>
user = 'https://github.com/shihai1991'

bugs.python.org fields:

activity = <Date 2021-07-31.15:02:13.673>
actor = 'fbidu'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2021-07-28.18:07:12.899>
creator = 'shihai1991'
dependencies = []
files = []
hgrepos = []
issue_num = 44766
keywords = ['patch']
message_count = 1.0
messages = ['398411']
nosy_count = 3.0
nosy_names = ['docs@python', 'fbidu', 'shihai1991']
pr_nums = ['27509']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue44766'
versions = ['Python 3.11']