chore: Use --no-cache-dir flag to pip in Dockerfiles, to save space

Using "--no-cache-dir" flag in pip install ,make sure dowloaded packages
by pip don't cached on system . This is a best practise which make sure
to fetch ftom repo instead of using local cached one . Further , in case
of Docker Containers , by restricing caching , we can reduce image size.
In term of stats , it depends upon the number of python packages
multiplied by their respective size . e.g for heavy packages with a lot
of dependencies it reduce a lot by don't caching pip packages.

Further , more detail information can be found at

https://medium.com/sciforce/strategies-of-docker-images-optimization-2ca9cc5719b6

Signed-off-by: Pratik Raj <rajpratik71@gmail.com>

routersploit/Dockerfile

@@ -20,7 +20,7 @@ RUN set -xe \
                   tar \
     && curl -sSL https://bootstrap.pypa.io/get-pip.py | python \
     && curl -sSL https://github.com/reverse-shell/routersploit/archive/master.tar.gz | tar xz --strip 1 \
-    && pip install -r requirements.txt \
+    && pip install --no-cache-dir -r requirements.txt \
     && apk del bash \
                build-base \
                curl \

routersploit/Dockerfile.arm

@@ -20,7 +20,7 @@ RUN set -xe \
                   tar \
     && curl -sSL https://bootstrap.pypa.io/get-pip.py | python \
     && curl -sSL https://github.com/reverse-shell/routersploit/archive/master.tar.gz | tar xz --strip 1 \
-    && pip install -r requirements.txt \
+    && pip install --no-cache-dir -r requirements.txt \
     && apk del bash \
                build-base \
                curl \