Documentation Fixes: Grammatical Corrections and Typo Fixes Across Multiple Files

[joaolago1113]

This pull request addresses multiple grammatical errors and typos across various documentation files in the project. The corrections improve readability and clarity, ensuring the documentation accurately reflects the intended meaning.

Changes Made

1. Commit 9795222

   • File: vms/platformvm/docs/validators_versioning.md
   • Corrections:
     • Changed 'its' to 'it's' and 'validator lifetime' to 'validator's lifetime' to correctly indicate possession.

2. Commit 994204f

   • File: vms/rpcchainvm/runtime/README.md
   • Correction:
     • Fixed typo 'instanace' to 'instance' in the 'Sending an Avalanche Warp Message' section.

3. Commit d635315

   • File: vms/example/xsvm/README.md
   • Correction:
     • Amended 'it's own chain' to 'its own chain' for grammatical accuracy.

4. Commit c8980f3

   • Files: tests/e2e/README.md and vms/proposervm/README.md
   • Corrections:
     • Changed 'an temporary network' to 'a temporary network' and corrected 'PChainHeight' description for clarity and grammatical correctness.

5. Commit 9f76ce8

   • File: network/README.md
   • Correction:
     • Rectified 'An node' to 'A node' in the last section for grammatical accuracy.

6. Commit 08f6094

   • File: CONTRIBUTING.md
   • Correction:
     • Fixed the spelling error 'modfiication' to 'modification' in the 'How to Contribute to Avalanche' section.

[StephenButtolph]

Thanks!