feat(web): Relax GrpcWebService request body type #3641

Job	Run time
check-external-types	23s
clippy	49s
check (ubuntu-latest)	2m 9s
codegen	20s
check (macOS-latest)	1m 51s
cargo-deny check	24s
check (windows-latest)	4m 42s
Interop Tests (ubuntu-latest)	32s
Interop Tests (macOS-latest)	43s
Check MSRV	25s
Interop Tests (windows-latest)	2m 35s
rustfmt	8s
semver	1m 3s
test (ubuntu-latest)	2m 41s
Check unused dependencies	3m 53s
test (macOS-latest)	2m 37s
test (windows-latest)	4m 46s
	30m 1s

Provide feedback