forge--set-topic-title(gitlab): Fix regression #228

Job	Run time
Compile / Get matrix	2m 53s
Compile / Compile using Emacs 29.1	1m 49s
Compile / Compile using Emacs 28.2	1m 54s
Compile / Compile using Emacs 28.1	1m 50s
Compile / Compile using Emacs 27.2	2m 1s
Compile / Compile using Emacs 27.1	1m 46s
Compile / Compile using Emacs 26.3	1m 45s
Compile / Compile using Emacs 26.2	1m 47s
Compile / Compile using Emacs 26.1	1m 56s
Compile / Compile using Emacs 25.3	1m 52s
Compile / Compile using Emacs 25.1	1m 50s
Compile / Compile using Emacs release-snapshot	1m 49s
Compile / Compile using Emacs snapshot	1m 28s
	24m 40s

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