Limit `ink_eth_compatibility` crate keywords to five (#966)

Otherwise crates.io refrains from publishing:

	invalid upload request: invalid length 6, expected at most 5 keywords per crate
20 jobs for v3.0.0-rc6 in 16 minutes and 19 seconds (queued for 6 seconds)
latest
Status Job ID Name Coverage
  Check
passed #1180333
linux-docker
check-std

00:01:52

passed #1180334
linux-docker
check-wasm

00:01:21

 
  Workspace
passed #1180335
linux-docker
build-std

00:02:16

passed #1180336
linux-docker
build-wasm

00:01:42

passed #1180341
linux-docker
clippy-std

00:02:10

passed #1180342
linux-docker
clippy-wasm

00:01:23

passed #1180340
linux-docker
codecov

00:05:26

passed #1180338
linux-docker
docs

00:01:09

passed #1180343
linux-docker
fmt

00:00:50

passed #1180339
linux-docker
spellcheck

00:00:14

passed #1180337
linux-docker
test

00:03:42

 
  Examples
passed #1180347
linux-docker
examples-clippy-std

00:01:03

passed #1180348
linux-docker
examples-clippy-wasm

00:00:55

passed #1180349
linux-docker
examples-contract-build

00:07:52

passed #1180350
linux-docker
examples-contract-build-delegator

00:03:34

passed #1180351
linux-docker
examples-docs

00:01:23

passed #1180346
linux-docker
examples-fmt

00:00:13

passed #1180344
linux-docker
examples-test

00:01:36

passed #1180345
linux-docker
examples-test-experimental-engine

00:00:58

 
  Ink Waterfall
failed #1180352
kubernetes-parity-build allowed to fail
ink-waterfall

00:00:55

 
Name Stage Failure
failed
ink-waterfall Ink Waterfall

Triggered pipeline status is running

Triggered pipeline status is running

Triggered pipeline status is failed
Something's broken in: "https://gitlab.parity.io/parity/ink-waterfall/-/pipelines/162676"
Cleaning up file based variables
ERROR: Job failed: command terminated with exit code 1