Fix wasm32 build by gating MultiFileSession on non-wasm targets #32615

Job	Run time
Python (lint)	40s
validate-workflow-yaml	5s
lint-toml	6s
Python (test)	2m 11s
Check build with minimal dependencies	2m 4s
Rust build (default features)	2m 28s
Rust build (with tokio dispatcher)	45s
Rust build (all-features)	2m 43s
Rust build (wasm32 with default features)	52s
Java	2m 32s
C++ build	1m 16s
License Check and Audit Check (bans licenses sources)	46s
C API test build	37s
C/C++ (lint)	5s
Check generated source files are up to date	42s
WASM integration smoke test	5m 35s
Rust (lint, no default)	2m 22s
License Check and Audit Check (advisories)	51s
Mirror DuckDB to R2 / Resolve DuckDB version and check R2	7s
DuckDB libraries available in R2	2s
Mirror DuckDB to R2 / Mirror DuckDB ${{ matrix.archive }} to R2	0s
Rust tests (linux-arm64)	4m 30s
Rust (lint)	2m 10s
SQL logic tests	2m 1s
Rust (docs)	2m 41s
Rust tests (windows-x64)	7m 50s
	46m 1s

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