[3.8] Remove extraneous ')' in abstract.h (GH-19146)

[miss-islington]

(cherry picked from commit ac2cfe6)

Co-authored-by: Jimmy Yang codingExpert123@gmail.com

[the-knights-who-say-ni]

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[miss-islington]

@marethyu12 and @terryjreedy: Status check is done, and it's a success ✅ .

[miss-islington]

@marethyu12 and @terryjreedy: Status check is done, and it's a success ✅ .

[miss-islington]

@marethyu12 and @terryjreedy: Status check is done, and it's a success ✅ .

[bedevere-bot]

@terryjreedy: Please replace # with GH- in the commit message next time. Thanks!