Use code font for tool names and flags in INSTALL.md.

[iphydf]

This change is 

[codecov]

Codecov Report

Merging #1134 into master will increase coverage by 0.1%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master   #1134     +/-   ##
========================================
+ Coverage    82.6%   82.8%   +0.1%     
========================================
  Files          82      81      -1     
  Lines       14473   14437     -36     
========================================
- Hits        11969   11956     -13     
+ Misses       2504    2481     -23

Impacted Files	Coverage Δ
toxav/audio.c	65.7% <0%> (-7.8%)	⬇️
auto_tests/toxav_many_test.c	92.5% <0%> (-4.1%)	⬇️
auto_tests/dht_test.c	47.1% <0%> (-0.8%)	⬇️
toxcore/onion_client.c	94.4% <0%> (-0.7%)	⬇️
toxcore/friend_connection.c	94.5% <0%> (-0.3%)	⬇️
toxcore/DHT.c	76.6% <0%> (-0.2%)	⬇️
toxcore/mono_time.c	92.8% <0%> (ø)	⬆️
auto_tests/conference_double_invite_test.c	100% <0%> (ø)	⬆️
auto_tests/lossy_packet_test.c	100% <0%> (ø)	⬆️
auto_tests/overflow_sendq_test.c	100% <0%> (ø)	⬆️
... and 16 more

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[sudden6]

Reviewed 1 of 1 files at r1.
Reviewable status: 0 of 1 approvals obtained