Fix `Pointer#+(offset: Int64)` doc parameter name typo #10977

Job	Run time
check_format	1m 53s
x86_64-gnu-test (1.7.3)	34m 35s
x86_64-gnu-test (1.8.2)	33m 41s
x86_64-gnu-test-preview_mt	5m 49s
x86_64-musl-test	38m 29s
x86_64-gnu-test (1.9.2)	32m 34s
x86_64-gnu-test (1.10.1)	32m 29s
x86_64-gnu-test (1.11.2)	32m 28s
deploy_api_docs	0s
x86_64-gnu-test (1.0.0, FLAGS=-Dwithout_ffi USE_PCRE1=true)	31m 40s
x86_64-gnu-test (1.1.1, FLAGS=-Dwithout_ffi USE_PCRE1=true)	33m 7s
x86_64-gnu-test (1.2.2, USE_PCRE1=true)	33m 54s
x86_64-gnu-test (1.3.2, USE_PCRE1=true)	33m 22s
x86_64-gnu-test (1.4.1, USE_PCRE1=true)	32m 45s
x86_64-gnu-test (1.5.1, USE_PCRE1=true)	33m 18s
x86_64-gnu-test (1.6.2, USE_PCRE1=true)	31m 47s
	7h 21m 51s

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