[amber-docs] RFR: Update towards-member-patterns.md -- Fixing typos

[David Alayachew]

Fixing some typos.

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Commit messages:
 - Update towards-member-patterns.md -- Fixing typos

Changes: https://git.openjdk.org/amber-docs/pull/22/files
 Webrev: https://webrevs.openjdk.org/?repo=amber-docs&pr=22&range=00
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/amber-docs/pull/22.diff
  Fetch: git fetch https://git.openjdk.org/amber-docs.git pull/22/head:pull/22

PR: https://git.openjdk.org/amber-docs/pull/22