limit eth_getBlockByNumber

[ilovers]

• Targeted PR against correct branch (see CONTRIBUTING.md)

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.

• Wrote tests

• Updated relevant documentation (docs/)

• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md

• Reviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge PR #XYZ: [title]" (coding standards)

[codecov-commenter]

Codecov Report

Merging #166 (b252ecc) into dev (d736de5) will increase coverage by 0.00%.
The diff coverage is 0.00%.

❗ Current head b252ecc differs from pull request most recent head 9e63937. Consider uploading reports for the commit 9e63937 to get more accurate results

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@@           Coverage Diff           @@
##              dev     #166   +/-   ##
=======================================
  Coverage   34.21%   34.22%           
=======================================
  Files         423      423           
  Lines       44400    44400           
=======================================
+ Hits        15192    15194    +2     
+ Misses      28097    28096    -1     
+ Partials     1111     1110    -1     

Impacted Files	Coverage Δ
app/rpc/backend/backend.go	0.00% <0.00%> (ø)

... and 1 file with indirect coverage changes