Remove evil-temp-filename

With the previous change, this function just serves to obfuscate the use of
make-temp-file. It's probably clearer to use make-temp-file directly.

evil-test-helpers.el

@@ -383,10 +383,6 @@ is executed at the end."
        (goto-char (overlay-end ,overlay))
        (evil-test-text (or ,end-string ,string) nil nil ,after-predicate))))
 
-(defun evil-temp-filename ()
-  "Return an appropriate temporary filename."
-  (make-temp-file "evil-test"))
-
 (defmacro evil-with-temp-file (file-var content &rest body)
   "Create a temp file with CONTENT and bind its name to FILE-VAR within BODY.
 FILE-VAR must be a symbol which contains the name of the
@@ -398,7 +394,7 @@ while the temporary file exists. The temporary file is deleted at
 the end of the execution of BODY."
   (declare (indent 2)
            (debug (symbolp form body)))
-  `(let ((,file-var (evil-temp-filename)))
+  `(let ((,file-var (make-temp-file "evil-test")))
      (with-temp-file ,file-var
        ,(if (stringp content)
             `(insert ,content)

evil-tests.el

@@ -7445,23 +7445,23 @@ maybe we need one line more with some text\n")
         (":w")
         (file filename "line1\nline2\nline3\nline4\nline5\n"))))
   (ert-info ("Write current buffer to new file")
-    (let ((filename (evil-temp-filename)))
+    (let ((filename (make-temp-file "evil-test-write")))
       (evil-test-buffer
         "[l]ine1\nline2\nline3\nline4\nline5\n"
         (delete-file filename)
         ((vconcat ":w " filename [return]))
         (file filename "line1\nline2\nline3\nline4\nline5\n")
         (delete-file filename))))
   (ert-info ("Write part of a buffer")
-    (let ((filename (evil-temp-filename)))
+    (let ((filename (make-temp-file "evil-test-write")))
       (evil-test-buffer
         "[l]ine1\nline2\nline3\nline4\nline5\n"
         (delete-file filename)
         ((vconcat ":2,3w " filename [return]))
         (file filename "line2\nline3\n")
         (delete-file filename))))
   (ert-info ("Appending a file")
-    (let ((filename (evil-temp-filename)))
+    (let ((filename (make-temp-file "evil-test-write")))
       (evil-test-buffer
         "[l]ine1\nline2\nline3\nline4\nline5\n"
         (delete-file filename)