As announced in the 2.21.0 release notes, the experimental gRPC API v2
has been removed.

[CHANGE] web: Remove APIv2. #7935
[ENHANCEMENT] React UI: Implement missing TSDB head stats section. #7876
[ENHANCEMENT] UI: Add Collapse all button to targets page. #6957
[ENHANCEMENT] UI: Clarify alert state toggle via checkbox icon. #7936
[ENHANCEMENT] Add rule_group_last_evaluation_samples and
    prometheus_tsdb_data_replay_duration_seconds metrics. #7737 #7977
[ENHANCEMENT] Gracefully handle unknown WAL record types. #8004
[ENHANCEMENT] Issue a warning for 64 bit systems running 32 bit
    binaries. #8012
[BUGFIX] Adjust scrape timestamps to align them to the intended
    schedule, effectively reducing block size. Workaround for a regression
    in go1.14+. #7976
[BUGFIX] promtool: Ensure alert rules are marked as restored in unit
    tests. #7661
[BUGFIX] Eureka: Fix service discovery when compiled in 32-bit. #7964
[BUGFIX] Don't do literal regex matching optimisation when case
    insensitive. #8013
[BUGFIX] Fix classic UI sometimes running queries for instant query when
    in range query mode. #7984

Signed-off-by: Paul Spooren <mail@aparcar.org>