deps: update dependency com.google.protobuf:protobuf-bom to v3.15.5

[renovate-bot]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
com.google.protobuf:protobuf-bom (source)	3.15.3 -> 3.15.5

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Release Notes

protocolbuffers/protobuf

v3.15.5

Compare Source

Ruby

• Fixed quadratic memory use in array append (#​8379)

PHP

• Fixed quadratic memory use in array append (#​8379)

C++

• Do not disable RTTI by default in the CMake build (#​8377)

v3.15.4

Compare Source

Ruby

• Fixed SEGV when users pass nil messages (#​8363)
• Fixed quadratic memory usage when appending to arrays (#​8364)

C++

• Create a CMake option to control whether or not RTTI is enabled (#​8361)

PHP

• read_property() handler is not supposed to return NULL (#​8362)

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[codecov]

Codecov Report

Merging #399 (0691972) into master (70f3a50) will not change coverage.
The diff coverage is n/a.

@@ Coverage Diff @@## master #399 +/- ##
=========================================
Coverage 67.74% 67.74% Complexity 384 384 =========================================
Files 36 36 Lines 1981 1981 Branches 267 267 =========================================
Hits 1342 1342 Misses 531 531 Partials 108 108 

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