infrastructure: drop comments that restate the code beside them (#9681)

#### Brief overview of PR changes/additions
- Removed 8 comments that only repeated the statement or assertion
message next to them
- Kept 1 of the 16 identical copies of the `lua_next()` key-copy note in
`TLuaInterpreterMedia.cpp`
- Comment-only: zero code lines changed

#### Motivation for adding to Mudlet
Reading a comment and then the code that says the same thing is wasted
effort; the rationale comments that document real gotchas are all
untouched.

#### Other info (issues closed, discussion etc)
Result of a pass over the last month of commits on `development`. The
vast majority of comments added there explain *why* rather than restate
*what*, so this is deliberately a small diff.

**Test case:** `git diff development...HEAD` shows only comment lines
removed; build and test suites are unaffected.


Assisted-by: Claude:claude-opus-5
Signed-off-by: Vadim Peretokin <vadim.peretokin@mudlet.org>

test/SecureStringUtilsTest.cpp

@@ -143,22 +143,17 @@ void SecureStringUtilsTest::testSecureMemoryClearing()
     QString testString = "sensitive_data";
     QString originalContent = testString;
     
-    // Clear the string
     SecureStringUtils::secureStringClear(testString);
-    
-    // String should be empty after clearing
     QVERIFY(testString.isEmpty());
     QVERIFY(testString != originalContent);
-    
-    // Test QByteArray clearing
+
     QByteArray testArray = "sensitive_bytes";
     QByteArray originalArray = testArray;
-    
+
     SecureStringUtils::secureByteArrayClear(testArray);
     QVERIFY(testArray.isEmpty());
     QVERIFY(testArray != originalArray);
 
-    // Test std::string clearing
     std::string testStdString = "sensitive_std_data";
     std::string originalStdString = testStdString;