fix: overly-restrictive wasm cfg for keystore #1457

Job	Run time
WASM tests	3m 56s
Unix tests (ubuntu-latest, stable)	2m 41s
Unix tests (ubuntu-latest, nightly)	1m 58s
Windows tests (stable, x86_64-pc-windows-gnu)	5m 17s
Windows tests (stable, x86_64-pc-windows-msvc)	4m 16s
Unix tests (macos-13, stable)	3m 49s
Unix tests (macos-13, nightly)	4m 57s
Unix tests (macos-14, stable)	2m 19s
Unix tests (macos-14, nightly)	2m 28s
Windows tests (nightly, x86_64-pc-windows-gnu)	4m 44s
Windows tests (nightly, x86_64-pc-windows-msvc)	4m 59s
no-std build	47s
	42m 11s

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