Tests: Remove some temporary files when finished using them

Leaving files in /tmp uses memory, which accumulates over time if you do
something weird like leaving `run-tests` going all day long. :^)

Tests/AK/TestFormat.cpp

@@ -10,6 +10,7 @@
 #include <AK/StringBuilder.h>
 #include <AK/Vector.h>
 #include <math.h>
+#include <unistd.h>
 
 TEST_CASE(is_integral_works_properly)
 {
@@ -232,6 +233,8 @@ TEST_CASE(file_descriptor)
     EXPECT_EQ("Hello, World!\nfoobar\n"sv, StringView { buffer.span().trim(nread) });
 
     fclose(file);
+
+    unlink(filename);
 }
 
 TEST_CASE(floating_point_numbers)

Tests/LibCore/TestLibCoreIODevice.cpp

@@ -35,6 +35,7 @@ TEST_CASE(file_readline)
     file->close();
     outputfile->close();
     VERIFY(files_have_same_contents(path, output_path));
+    unlink(output_path);
 }
 
 TEST_CASE(file_get_read_position)
@@ -88,4 +89,5 @@ TEST_CASE(file_lines_range)
     file->close();
     outputfile->close();
     VERIFY(files_have_same_contents(path, output_path));
+    unlink(output_path);
 }