chore: remove obsolete decimal and div test files from test/number directory

The deleted test files covered decimal extraction and integer division behavior for the Wren language runtime. These tests are no longer relevant to the current codebase and have been removed to clean up the test suite.

test/number/decimal.wren

@@ -1,8 +0,0 @@
-IO.print(123.decimal)      // expect: 0
-IO.print((-123).decimal)   // expect: 0
-IO.print(0.decimal)        // expect: 0
-IO.print((-0).decimal)     // expect: -0
-IO.print(0.123.decimal)    // expect: 0.123
-IO.print(12.3.decimal)     // expect: 0.3
-IO.print((-0.123).decimal) // expect: -0.123
-IO.print((-12.3).decimal)  // expect: -0.3

test/number/div.wren

@@ -1,5 +0,0 @@
-IO.print((8).div(2))   // expect: 4
-IO.print((8.5).div(2)) // expect: 4
-IO.print((9).div(2))   // expect: 4
-IO.print((9.9).div(2)) // expect: 4
-IO.print((10).div(2))  // expect: 5