Update .gitignore (#5323)

In current master, after get.exe, there's tools/mkfatfs.exe that must be ignored.
Also cleaning up a simple duplicate line in .gitignore.
This is for Windows only, any hints on what can be done for Linux, Mac, is appreciated.

Author: dok-net

.gitignore

@@ -6,6 +6,7 @@ tools/esptool
 tools/esptool.exe
 tools/mkspiffs
 tools/mklittlefs
+tools/mkfatfs.exe
 .DS_Store
 
 #Ignore files built by Visual Studio/Visual Micro
@@ -17,4 +18,3 @@ __vm/
 .vscode/
 platform.sloeber.txt
 boards.sloeber.txt
-tools/mklittlefs