Update EIP-1015: Fix Typographical Errors

[Dimitrolito]

This pull request corrects several typographical errors across multiple EIP documents. The changes include the addition of hyphens in compound adjectives and the correction of article usage (i.e., "a" vs. "an").

Changes:

1. Added hyphen in "three-step" in EIP-101.
2. Corrected "six month" to "six-month" in EIP-1015.
3. Changed "a object" to "an object" in EIP-1186.
4. Added hyphen in "30-second" in EIP-1234.
5. Corrected "15 second" to "15-second" in EIP-1240.
6. Corrected "an unique" to "a unique" in EIP-1470.
7. Changed "a implementation" to "an implementation" in EIP-1485.
8. Corrected "a address" to "an address" in EIP-158.

[eth-bot]

File EIPS/eip-1470.md

Requires 1 more reviewers from @thec00n
Requires 1 more reviewers from @g11tech, @lightclient, @SamWilsn, @xinbenlv

File EIPS/eip-1015.md

Requires 1 more reviewers from @g11tech, @lightclient, @SamWilsn

File EIPS/eip-1186.md

Requires 1 more reviewers from @g11tech, @lightclient, @SamWilsn

[poojaranjan]

The proposed change to EIP-1234 is trivial and except for EIP-1234, all proposals are Stagnant.
As Stagnant proposals don't accept typo-related PRs, this PR can be closed.

[github-actions]

The commit d42f703 (as a parent of 0bb366e) contains errors.
Please inspect the Run Summary for details.