string: various fixes (#3814)

tests/stubtest_whitelists/py38.txt

@@ -167,9 +167,6 @@ signal.sigwaitinfo
 smtplib.SMTP.sendmail
 sre_constants.RANGE_IGNORE
 statistics.NormalDist.samples
-string.Formatter.format
-string.Template.safe_substitute
-string.Template.substitute
 sys.UnraisableHookArgs
 threading.ExceptHookArgs
 time.CLOCK_PROF

tests/stubtest_whitelists/py3_common.txt

@@ -710,7 +710,6 @@ ssl.SSLSocket.recvfrom_into
 ssl.SSLSocket.sendto
 ssl._ASN1Object.__new__
 statistics.median_grouped
-string.capwords
 subprocess.Popen.send_signal
 subprocess.call
 sunau.Au_write.getmark