Set version to 2.0.0-rc7

* Ignore python error about modifying system python (#4863)

Builds/containers/gitlab-ci/docker_alpine_setup.sh

@@ -10,6 +10,6 @@ apk add \
     bash util-linux coreutils binutils grep \
     make ninja cmake build-base gcc g++ abuild git \
     python3 python3-dev
-pip3 install awscli
+pip3 install awscli --break-system-packages
 # list curdir contents to build log:
 ls -la

src/ripple/protocol/impl/BuildInfo.cpp

@@ -33,7 +33,7 @@ namespace BuildInfo {
 //  and follow the format described at http://semver.org/
 //------------------------------------------------------------------------------
 // clang-format off
-char const* const versionString = "2.0.0-rc6"
+char const* const versionString = "2.0.0-rc7"
 // clang-format on
 
 #if defined(DEBUG) || defined(SANITIZER)