fix(punctuation): Add period instead of semicolon for Greek lang (@sledgehammer999) (monkeytypegame#6299)

### Description

This is a followup to PR monkeytypegame#6297.
1. `:` is a valid punctuation mark and isn't decided in another if/else
branch, so I left it as-is.
2. `;` is also a valid punctuation mark but it is used as a question
mark in the appropriate if/else branch. So here I convert it to a
period.

Modern greeks use either a period or a comma in place of a middle
dot/ano teleia. I would say that a period fits better most of the time.

### Checks

- [ ] Adding quotes?
- [ ] Make sure to include translations for the quotes in the
description (or another comment) so we can verify their content.
- [ ] Adding a language or a theme?
- [ ] If is a language, did you edit `_list.json`, `_groups.json` and
add `languages.json`?
  - [ ] If is a theme, did you add the theme.css?
- Also please add a screenshot of the theme, it would be extra awesome
if you do so!
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tag them below.
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Author: sledgehammer999

frontend/src/ts/test/words-generator.ts

@@ -204,6 +204,11 @@ export async function punctuateWord(
   ) {
     if (currentLanguage === "french") {
       word = ";";
+    } else if (currentLanguage === "greek") {
+      // Normally U+00B7 ('middle dot' or 'ano teleia') would be used here.
+      // However, a) it has fallen into disuse in contemporary times and
+      // b) there isn't a dedicated key on a keyboard to input it
+      word = ".";
     } else if (currentLanguage === "arabic" || currentLanguage === "kurdish") {
       word += "؛";
     } else if (currentLanguage === "chinese") {