remove bad CPU clock values from the menu

Author: me-no-dev

boards.txt

@@ -62,22 +62,10 @@ esp32.menu.CPUFreq.26=26MHz (26MHz XTAL)
 esp32.menu.CPUFreq.26.build.f_cpu=26000000L
 esp32.menu.CPUFreq.20=20MHz (40MHz XTAL)
 esp32.menu.CPUFreq.20.build.f_cpu=20000000L
-esp32.menu.CPUFreq.13=13MHz
+esp32.menu.CPUFreq.13=13MHz (26MHz XTAL)
 esp32.menu.CPUFreq.13.build.f_cpu=13000000L
 esp32.menu.CPUFreq.10=10MHz (40MHz XTAL)
 esp32.menu.CPUFreq.10.build.f_cpu=10000000L
-esp32.menu.CPUFreq.8=8MHz (40MHz XTAL)
-esp32.menu.CPUFreq.8.build.f_cpu=8000000L
-esp32.menu.CPUFreq.5=5MHz
-esp32.menu.CPUFreq.5.build.f_cpu=5000000L
-esp32.menu.CPUFreq.4=4MHz
-esp32.menu.CPUFreq.4.build.f_cpu=4000000L
-esp32.menu.CPUFreq.3=3MHz
-esp32.menu.CPUFreq.3.build.f_cpu=3000000L
-esp32.menu.CPUFreq.2=2MHz
-esp32.menu.CPUFreq.2.build.f_cpu=2000000L
-esp32.menu.CPUFreq.1=1MHz
-esp32.menu.CPUFreq.1.build.f_cpu=1000000L
 
 esp32.menu.FlashMode.qio=QIO
 esp32.menu.FlashMode.qio.build.flash_mode=dio