build readme nits

sudo is needed to rm FRESH_CLONE as docker is running as sudo.
the proper fix would be to have docker not run as sudo...

contrib/build-linux/appimage/README.md

@@ -25,7 +25,7 @@ see [issue #5159](https://github.com/spesmilo/electrum/issues/5159).
 2. Build image
 
     ```
-    $ sudo docker build --no-cache -t electrum-appimage-builder-img contrib/build-linux/appimage
+    $ sudo docker build -t electrum-appimage-builder-img contrib/build-linux/appimage
     ```
 
 3. Build binary

contrib/build-wine/README.md

@@ -32,7 +32,7 @@ folder.
 
     ```
     $ FRESH_CLONE=contrib/build-wine/fresh_clone && \
-        rm -rf $FRESH_CLONE && \
+        sudo rm -rf $FRESH_CLONE && \
         mkdir -p $FRESH_CLONE && \
         cd $FRESH_CLONE  && \
         git clone https://github.com/spesmilo/electrum.git && \