Fix duplicate glyphs3 GSMetrics; take the first and ignore 'filter' #3235

Job	Run time
Build GS and check the result	2m 58s
Rustfmt	1m 12s
cargo check no std	1m 30s
resources/scripts/ots_test.sh	1m 3s
cargo check wasm	1m 12s
Clippy lints	1m 26s
cargo test fea-rs	57s
fontbe tests	50s
fontc tests	1m 9s
tests other than fontbe,fontc	1m 22s
	13m 39s

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