Fixed broken links in ota_updates/readme.rst

Replaced links to filesystem.md with filesystem.rst

Author: mguntli

doc/ota_updates/readme.rst

@@ -57,7 +57,7 @@ Basic Requirements
 
 Flash chip size should be able to hold the old sketch (currently running) and the new sketch (OTA) at the same time.
 
-Keep in mind that the File system and EEPROM for example needs space too (one time) see `flash layout <../filesystem.md#flash-layout>`__.
+Keep in mind that the File system and EEPROM for example needs space too (one time) see `flash layout <../filesystem.rst#flash-layout>`__.
 
 .. code:: cpp
 
@@ -226,7 +226,7 @@ If this is the case, then most likely ESP module has not been reset after initia
 
 The most common causes of OTA failure are as follows: \* not enough physical memory on the chip (e.g. ESP01 with 512K flash memory is not enough for OTA), \* too much memory declared for SPIFFS so new sketch will not fit between existing sketch and SPIFFS – see `Update process - memory view <#update-process---memory-view>`__, \* too little memory declared in Arduino IDE for your selected board (i.e. less than physical size), \* not resetting the ESP module after initial upload using serial port.
 
-For more details regarding flash memory layout please check `File system <https://github.com/esp8266/Arduino/blob/master/doc/filesystem.md>`__. For overview where new sketch is stored, how it is copied and how memory is organized for the purpose of OTA see `Update process - memory view <#update-process---memory-view>`__.
+For more details regarding flash memory layout please check `File system <../filesystem.rst>`__. For overview where new sketch is stored, how it is copied and how memory is organized for the purpose of OTA see `Update process - memory view <#update-process---memory-view>`__.
 
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